Endura Flap Custom Thermo Panel 3e for Windows
- Durable Aluminum frame with pet door made to withstand extreme climates ranging in width from 11.25 -17.25 inches (see size chart below)
- Adjustable heights and custom sizes to fit any sliding window
- Made with dual-pane, Low-E glass to improve energy efficiency
-
Easy to install and doesn't require semi-permanent installation
- How to Measure Your Track Height video guide
-
Please allow 4 -6 weeks for custom models to be built
- Custom orders are made to your specifications and are non-returnable
- We'll need more information to complete your order. In your Order Confirmation email there is an Orange button with "Finish Your Order". Click on it to enter to answer questions to finish your order. Thank you!

Product Details
This is the custom window pet door for the Endura Flap Thermo Panel 3e for horizontal sliding windows of unusual heights. The track height adjustment ranges for custom orders are for windows under 74 3/4", between 80 1/4" 93 1/4", and over 96 1/4". Please note that custom-made Endura doors are non-refundable and non-returnable. The panels have a 3" spring-loaded height adjustment, so if you request a 40" panel, for example, the panel you receive will be adjustable from 38" to 41". The Thermo Panel 3e has a spring-loaded design that fits into your sliding window track without requiring the use of any tools. It features dual-pane, Low-E glass to prevent UV rays and infrared light from entering your home. With a flexible, environmentally friendly flap lined on all three sides with magnets, heavy wind will be unable to blow through this window pet door. Save on heating and cooling with the insulating Endura Flap.
Features:
- Pet flaps come in small, medium, large, & extra large for any size pet
- Flap dimensions designed to accommodate pets of multiple sizes
- Aluminum frame designed to fit into the window track with a width of at least 1" thick
- Available in white, brushed aluminum, and dark bronze (black)
- Dual-pane, Low-E glass allows natural light to enter while blocking out unwanted UV rays and infrared light
- Flap withstands -40 degree temperatures and stays sealed in 50mph winds
- Magnetic sealing resists heavy winds/storms
- Flap swings on a rod at the top, avoiding breakage
- Includes a sturdy locking cover
- C-Clamp Lock included for adjustment ranges under 74 3/4" to lock the slider
Benefits:
- Removable panel benefits all owners, especially renters.
- Don't have to make any permanent alterations to window
- Available in white, bronze, or brushed aluminum to match your window
- Pets can enter and exit as they please
Size Chart


Flap Size | Flap Dimension | Step Over Range | Overall Panel Width |
---|---|---|---|
Small #6 | 6" w x 11" h | 3" – 5" | 11 1⁄4" |
Medium #8 | 8" w x 15" h | 3" – 5" | 13 1⁄4" |
Large #10 | 10" w x 19" h | 3" – 5" | 15 1⁄4" |
Extra Large #12 | 12" w x 23" h | 3" – 7" (ships at 5") | 17 1⁄4" |
Track Height Adjustment range is based on the measurement of your window height from the lowest point of your track to the highest point. Wondering how to measure your track? Review our Track Measuring Guide. Each Endura Flap Thermo Panel 3e for Windows has a 3" adjustment range with your window track height approximately in the middle.
Please note: If you order a custom insulated glass unit, it must be specially ordered which takes about 4 weeks. Since these are custom heights it is a final sale, no returns.
If your measured track height is near the bottom of the adjustment range then you should review A Note of Caution.
Minimum and Maximum heights vary by flap size. Here is the info:
Custom Height: Minimum & Maximum Heights | ||
---|---|---|
Model | Minimum | Maximum |
Small | 35" | 100" |
Medium | 42" | 107" |
Large | 48" | 117" |
Extra Large | 46" | 123" |
Installation Instructions
Parts
- Panel Pet Door
- Foam Weather Strip
- Center Post Weather Seal Draft Stopper
- Sliding Door C-Clamp Lock
Tools
- None
Please read instructions & notes thoroughly before installation.
One-Piece Panel
Step 1: Step Over Adjust the Step Over (Optional)

- The top of the flap should be positioned to be at least 1” above the top of the pet’s shoulder.
- If the factory setting is not suitable, please adjust it before proceeding. If the current setting is suitable, proceed to the “Installation Instructions” section.
Step 2 Adjust the Screws

- Lay the entire panel on a flat surface.
- Using a #2 Philips head screwdriver, remove the bottom side-screws and loosen the upper side-screws. Screws were tightly installed to hold the panel together during shipping; a power tool* is recommended.
Step 3 Adjust the Spacers

- Once the bottom screws have been removed and the upper side-screws loosened, the Pet Door Assembly and spacers can be removed by sliding the sections down and out of the panel.
Step 4 Replace the Spacers

- Replace the spacers and the Pet Door Assembly by sliding them back in a different order to achieve the desired height. You can move the spacer below and above the flap to raise or lower the flap height.
Step 5 Tighten the Screws
- When finished, replace the bottom side-screws and tighten the next upper-side screws.
Step 1: Install the Panel Spring Mechanism

- Loosen the height adjustment locks at the top of the pet panel. This allows the spring mechanism to move freely up and down.
Step 2 Test Fit the Panel in Your Track

- To insert the panel into the top track, push up against the spring mechanism and swing the bottom of the panel up and over the threshold.
- Seat the panel on top of the small guide rail in the track.
Step 3 Apply the Weatherstripping

- Once you’re sure the panel fits, remove it from the frame and lay it on its side on the ground.
- Apply the foam weather-stripping by peeling back the paper and exposing the adhesive.
- Unroll it along the edge of the panel, pressing to ensure it adheres. Install on both sides, trim it fit with scissors.
Step 4 Install the Draft Stopper

- The center post weather seal strip (draft stopper) should be installed on the inside of the home.
- Trim with scissors as needed. Clean the edge of your patio door with rubbing alcohol before installing to assure a good seal.
- Repeat step two to install the panel in your track.
Parts
- Top Glass Panel Section
- Bottom Flap Section
- Foam Weather Strip
- Center Post Weather Seal Draft Stopper
- 4 Flathead Screws
- Flathead Screwdriver
- Sliding Door C-Clamp Lock
Tools
- None
Please read instructions & notes thoroughly before installation.
Two-Piece Panel
Step 1: Step Over Adjust Step Over Height (Optional)

- The top of the flap should be positioned to be at least 1” above the top of the pet’s shoulder.
- If the factory setting is not suitable, please adjust it before proceeding. If the current setting is suitable, proceed to the “Installation Instructions” section.
Step 2 Rearrange the Pieces

- Simply slide the pieces up and out from the bottom half of your panel to rearrange.
- Loosen a bottom screw if the pieces are too snug to move.
Step 3 Reconnect the Pieces
- Replace the spacers and the Pet Door Assembly by sliding them back in a different order to achieve the desired height.
- You can move the spacer below or above the flap to raise or lower the flap height.
Step 4 Screw the Pieces Together
- The order of the pieces is important! The piece on the bottom needs to always be at the bottom, as that is where the screws attach. You can now assemble the patio panel!
Step 1: Connect the Sections Align the Connectors

- Align the aluminum connectors extending from the bottom flap panel section with the top glass panel section.
- Press the aluminum connectors into the holes at the bottom of the top glass panel section.
- Ensure locking cover & height adjustment locks are on the same side!
Step 2 Tap the Pieces Together

- Gently tap the bottom surface of the panel against the ground to completely insert the connectors.
- Protect hard surfaces to prevent scratching.
- The components of the panel are designed to slide together very tightly.
Step 3 Secure the Sections

- Fasten the two panels together using the four flathead screws and countersunk washers found in the panel packaging.
- Use the included flathead screwdriver to tighten flathead screws and countersunk washers so the two halves of the door are pulled together.
Step 1: Install the Panel Adjust Spring Mechanism

- Loosen the height adjustment locks at the top of the pet panel. This allows the spring mechanism to move freely up and down.
Step 2 Test Fit the Panel in Your Track

- To insert the panel into the top track, push up against the spring mechanism and swing the bottom of the panel up and over the threshold.
- Seat the panel on top of the small guide rail in the track.
Step 3 Apply the Weatherstripping

- Once you’re sure the panel fits, remove it from the frame and lay it on its side on the ground.
- Apply the foam weather-stripping by peeling back the paper and exposing the adhesive.
- Unroll it along the edge of the panel, pressing to ensure it adheres. Install on both sides, trim it fit with scissors.
- Repeat step two to install the panel in your track.
Step 4 Install the Draft Stopper

- The center post weather seal strip (draft stopper) should be installed on the inside of the home.
- Trim with scissors as needed. Clean the edge of your patio door with rubbing alcohol before installing to assure a good seal.
Lock Details

Since you cannot lock your sliding door to your panel pet door, we have provided you with alternative locking methods to secure your home:
Installing the sliding door clamp: This clamp has a screw that tightens by hand to prevent the sliding door from moving beyond the clamp’s placement. For doors manufactured with the glass slider on the inside track, the lock can usually be installed on the door’s raised track.
If you aren’t able to use the lock that comes with the panel: A great alternative to locking your sliding glass door is a Charley bar or dowel in the track. Both work off the same concept – they block the slider from opening. When engaged you cannot pull the sliding door away from the pet door panel.

Other Installation Options
Semi-Permanent Installation:
You might choose to secure the panel in your track with screws. This can be done by drilling screws at an angle in the top and bottom tracks. We recommend doing this from the outside to minimize damage to the sliding glass door frame. One-way screws will prevent tampering or removal of the panel from the outside.

Stationary Panel:
Some stationary sliding door panels can be unfastened and moved over to one side so that you can install the pet door panel between the jamb and stationary panel.
Avoid damaging your sliding glass door by checking that your door can move and that you can reinstall it properly before trying to uninstall the unit.
You will still lose space in your slider to move through, however, you will be able to use your existing sliding door lock to secure your home. Installing your pet door this way is also great in that you already have an alarm system in place.
If your sliding glass door slides on the outside track, using an alternative lock might not be possible, so this allows you to still lock your door.
NOTE: You can do the stationary panel install with the regular spring actuator method – no need to screw it in.
Videos
The Endura Flap Pet Door
The Thermo Panel 3e Patio Panel Pet Door
Removing Side Magnets
How to Adjust Your Endura Flap Magnet Strength
Adjusting the Step Over Height
FAQ
Which flap size should I get? Here is a measurement guide to help you out. |
What do I measure? You would need to measure from the deepest part in the bottom track to the deepest part up inside the top track. Also the panel is 1" in thickness so make sure that your track is at least that wide to be able to accept the panel. |
What is the step-over? That is how far from the bottom of the doggy door the flap actually starts. So it is what your pet would have to comfortably clear in order to get out and in. |
Is this dog door insert going to provide good insulation? These are excellent for insulation as they have dual pane Low-E glass, and the Endura flap pet door which happens to be one of the best sealing and energy-efficient doors on the market. |
Can I install this myself? This is a good door for DIY home installations. Its user-adjustable design allows it to have an easy installation process. In the taller heights, it can be a bit tricky since the panel is larger and heavier, so it is helpful to have an extra set of hands. I would suggest taking a look at the videos tab for a better idea of just what the installation looks like. |
Can I lock the doggie door? Yep! We include a well-made closing cover that you slide in place. The tracks are located inside so you don't have to go outside in bad weather to close it off. |
How do I lock the sliding door for security? We include a clamp lock for panels under 80.25". You can also use a Charley bar or the old dowel in the track method. All of these different mechanisms work off the same principle that when in place at the window jamb, will prevent the sliding door from being pulled away from the pet door panel. |
Can the patio pet door panel be taken out from the outside? No, the panel is held in at the top with a spring loaded adjustment piece. Once the thumb screws, located on the inside, are tightened you can't slide down that piece in order to remove it. |
What is the panel made of? The framing is a heavy gauge aluminum. |
Can I get this with a flap door that keeps other animals out? We do have the Thermo Panel 2e panels, but the largest flap is on 7" x 7" in Pet Door version. So it is recommend more for cats and pretty small dogs. |
How long do these take? Being that they are custom and we have to special order the glass, it can take roughly 4 weeks for delivery. |
I live in a mobile home with a shorter than normal sliding glass door. Can I get a custom thermo panel? Yes, you can order a Thermo Panel to accommodate your shorter door. When choosing the Track Height Adjustment Range, select "cust ht under 74 3/4" and then you will be prompted to enter your track height. We will build a panel to your specifications. |
I ordered my door but the door frame is too short for my window. What do I do? You can order a height extension panel from Endura Flap Pet Products that will fit into your door track and add extra height to your Thermo Panel. |
Where can I purchase a replacement flap for this door? You can purchase a replacement flap for small to extra large door sizes. You can see our full list of replacement parts and accessories for other brands like Ideal Pet Supplies and Petsafe here. |
How much does shipping cost? Shipping is calculated at checkout. |
Warranty
Endura Flap products have a lifetime warranty against defects in materials and workmanship under standard regular use. Damage caused by not using the product as intended, improper installation, and chewing is not covered under this warranty.
Customer Reviews

Size Chart


Flap Size | Flap Dimension | Step Over Range | Overall Panel Width |
---|---|---|---|
Small #6 | 6" w x 11" h | 3" – 5" | 11 1⁄4" |
Medium #8 | 8" w x 15" h | 3" – 5" | 13 1⁄4" |
Large #10 | 10" w x 19" h | 3" – 5" | 15 1⁄4" |
Extra Large #12 | 12" w x 23" h | 3" – 7" (ships at 5") | 17 1⁄4" |
Track Height Adjustment range is based on the measurement of your window height from the lowest point of your track to the highest point. Wondering how to measure your track? Review our Track Measuring Guide. Each Endura Flap Thermo Panel 3e for Windows has a 3" adjustment range with your window track height approximately in the middle.
Please note: If you order a custom insulated glass unit, it must be specially ordered which takes about 4 weeks. Since these are custom heights it is a final sale, no returns.
If your measured track height is near the bottom of the adjustment range then you should review A Note of Caution.
Minimum and Maximum heights vary by flap size. Here is the info:
Custom Height: Minimum & Maximum Heights | ||
---|---|---|
Model | Minimum | Maximum |
Small | 35" | 100" |
Medium | 42" | 107" |
Large | 48" | 117" |
Extra Large | 46" | 123" |
Installation Instructions
Parts
- Panel Pet Door
- Foam Weather Strip
- Center Post Weather Seal Draft Stopper
- Sliding Door C-Clamp Lock
Tools
- None
Please read instructions & notes thoroughly before installation.
One-Piece Panel
Step 1: Step Over Adjust the Step Over (Optional)

- The top of the flap should be positioned to be at least 1” above the top of the pet’s shoulder.
- If the factory setting is not suitable, please adjust it before proceeding. If the current setting is suitable, proceed to the “Installation Instructions” section.
Step 2 Adjust the Screws

- Lay the entire panel on a flat surface.
- Using a #2 Philips head screwdriver, remove the bottom side-screws and loosen the upper side-screws. Screws were tightly installed to hold the panel together during shipping; a power tool* is recommended.
Step 3 Adjust the Spacers

- Once the bottom screws have been removed and the upper side-screws loosened, the Pet Door Assembly and spacers can be removed by sliding the sections down and out of the panel.
Step 4 Replace the Spacers

- Replace the spacers and the Pet Door Assembly by sliding them back in a different order to achieve the desired height. You can move the spacer below and above the flap to raise or lower the flap height.
Step 5 Tighten the Screws
- When finished, replace the bottom side-screws and tighten the next upper-side screws.
Step 1: Install the Panel Spring Mechanism

- Loosen the height adjustment locks at the top of the pet panel. This allows the spring mechanism to move freely up and down.
Step 2 Test Fit the Panel in Your Track

- To insert the panel into the top track, push up against the spring mechanism and swing the bottom of the panel up and over the threshold.
- Seat the panel on top of the small guide rail in the track.
Step 3 Apply the Weatherstripping

- Once you’re sure the panel fits, remove it from the frame and lay it on its side on the ground.
- Apply the foam weather-stripping by peeling back the paper and exposing the adhesive.
- Unroll it along the edge of the panel, pressing to ensure it adheres. Install on both sides, trim it fit with scissors.
Step 4 Install the Draft Stopper

- The center post weather seal strip (draft stopper) should be installed on the inside of the home.
- Trim with scissors as needed. Clean the edge of your patio door with rubbing alcohol before installing to assure a good seal.
- Repeat step two to install the panel in your track.
Parts
- Top Glass Panel Section
- Bottom Flap Section
- Foam Weather Strip
- Center Post Weather Seal Draft Stopper
- 4 Flathead Screws
- Flathead Screwdriver
- Sliding Door C-Clamp Lock
Tools
- None
Please read instructions & notes thoroughly before installation.
Two-Piece Panel
Step 1: Step Over Adjust Step Over Height (Optional)

- The top of the flap should be positioned to be at least 1” above the top of the pet’s shoulder.
- If the factory setting is not suitable, please adjust it before proceeding. If the current setting is suitable, proceed to the “Installation Instructions” section.
Step 2 Rearrange the Pieces

- Simply slide the pieces up and out from the bottom half of your panel to rearrange.
- Loosen a bottom screw if the pieces are too snug to move.
Step 3 Reconnect the Pieces
- Replace the spacers and the Pet Door Assembly by sliding them back in a different order to achieve the desired height.
- You can move the spacer below or above the flap to raise or lower the flap height.
Step 4 Screw the Pieces Together
- The order of the pieces is important! The piece on the bottom needs to always be at the bottom, as that is where the screws attach. You can now assemble the patio panel!
Step 1: Connect the Sections Align the Connectors

- Align the aluminum connectors extending from the bottom flap panel section with the top glass panel section.
- Press the aluminum connectors into the holes at the bottom of the top glass panel section.
- Ensure locking cover & height adjustment locks are on the same side!
Step 2 Tap the Pieces Together

- Gently tap the bottom surface of the panel against the ground to completely insert the connectors.
- Protect hard surfaces to prevent scratching.
- The components of the panel are designed to slide together very tightly.
Step 3 Secure the Sections

- Fasten the two panels together using the four flathead screws and countersunk washers found in the panel packaging.
- Use the included flathead screwdriver to tighten flathead screws and countersunk washers so the two halves of the door are pulled together.
Step 1: Install the Panel Adjust Spring Mechanism

- Loosen the height adjustment locks at the top of the pet panel. This allows the spring mechanism to move freely up and down.
Step 2 Test Fit the Panel in Your Track

- To insert the panel into the top track, push up against the spring mechanism and swing the bottom of the panel up and over the threshold.
- Seat the panel on top of the small guide rail in the track.
Step 3 Apply the Weatherstripping

- Once you’re sure the panel fits, remove it from the frame and lay it on its side on the ground.
- Apply the foam weather-stripping by peeling back the paper and exposing the adhesive.
- Unroll it along the edge of the panel, pressing to ensure it adheres. Install on both sides, trim it fit with scissors.
- Repeat step two to install the panel in your track.
Step 4 Install the Draft Stopper

- The center post weather seal strip (draft stopper) should be installed on the inside of the home.
- Trim with scissors as needed. Clean the edge of your patio door with rubbing alcohol before installing to assure a good seal.
Lock Details

Since you cannot lock your sliding door to your panel pet door, we have provided you with alternative locking methods to secure your home:
Installing the sliding door clamp: This clamp has a screw that tightens by hand to prevent the sliding door from moving beyond the clamp’s placement. For doors manufactured with the glass slider on the inside track, the lock can usually be installed on the door’s raised track.
If you aren’t able to use the lock that comes with the panel: A great alternative to locking your sliding glass door is a Charley bar or dowel in the track. Both work off the same concept – they block the slider from opening. When engaged you cannot pull the sliding door away from the pet door panel.

Other Installation Options
Semi-Permanent Installation:
You might choose to secure the panel in your track with screws. This can be done by drilling screws at an angle in the top and bottom tracks. We recommend doing this from the outside to minimize damage to the sliding glass door frame. One-way screws will prevent tampering or removal of the panel from the outside.

Stationary Panel:
Some stationary sliding door panels can be unfastened and moved over to one side so that you can install the pet door panel between the jamb and stationary panel.
Avoid damaging your sliding glass door by checking that your door can move and that you can reinstall it properly before trying to uninstall the unit.
You will still lose space in your slider to move through, however, you will be able to use your existing sliding door lock to secure your home. Installing your pet door this way is also great in that you already have an alarm system in place.
If your sliding glass door slides on the outside track, using an alternative lock might not be possible, so this allows you to still lock your door.
NOTE: You can do the stationary panel install with the regular spring actuator method – no need to screw it in.
Videos
The Endura Flap Pet Door
The Thermo Panel 3e Patio Panel Pet Door
Removing Side Magnets
How to Adjust Your Endura Flap Magnet Strength
Adjusting the Step Over Height
FAQ
Which flap size should I get? Here is a measurement guide to help you out. |
What do I measure? You would need to measure from the deepest part in the bottom track to the deepest part up inside the top track. Also the panel is 1" in thickness so make sure that your track is at least that wide to be able to accept the panel. |
What is the step-over? That is how far from the bottom of the doggy door the flap actually starts. So it is what your pet would have to comfortably clear in order to get out and in. |
Is this dog door insert going to provide good insulation? These are excellent for insulation as they have dual pane Low-E glass, and the Endura flap pet door which happens to be one of the best sealing and energy-efficient doors on the market. |
Can I install this myself? This is a good door for DIY home installations. Its user-adjustable design allows it to have an easy installation process. In the taller heights, it can be a bit tricky since the panel is larger and heavier, so it is helpful to have an extra set of hands. I would suggest taking a look at the videos tab for a better idea of just what the installation looks like. |
Can I lock the doggie door? Yep! We include a well-made closing cover that you slide in place. The tracks are located inside so you don't have to go outside in bad weather to close it off. |
How do I lock the sliding door for security? We include a clamp lock for panels under 80.25". You can also use a Charley bar or the old dowel in the track method. All of these different mechanisms work off the same principle that when in place at the window jamb, will prevent the sliding door from being pulled away from the pet door panel. |
Can the patio pet door panel be taken out from the outside? No, the panel is held in at the top with a spring loaded adjustment piece. Once the thumb screws, located on the inside, are tightened you can't slide down that piece in order to remove it. |
What is the panel made of? The framing is a heavy gauge aluminum. |
Can I get this with a flap door that keeps other animals out? We do have the Thermo Panel 2e panels, but the largest flap is on 7" x 7" in Pet Door version. So it is recommend more for cats and pretty small dogs. |
How long do these take? Being that they are custom and we have to special order the glass, it can take roughly 4 weeks for delivery. |
I live in a mobile home with a shorter than normal sliding glass door. Can I get a custom thermo panel? Yes, you can order a Thermo Panel to accommodate your shorter door. When choosing the Track Height Adjustment Range, select "cust ht under 74 3/4" and then you will be prompted to enter your track height. We will build a panel to your specifications. |
I ordered my door but the door frame is too short for my window. What do I do? You can order a height extension panel from Endura Flap Pet Products that will fit into your door track and add extra height to your Thermo Panel. |
Where can I purchase a replacement flap for this door? You can purchase a replacement flap for small to extra large door sizes. You can see our full list of replacement parts and accessories for other brands like Ideal Pet Supplies and Petsafe here. |
How much does shipping cost? Shipping is calculated at checkout. |
Warranty
Endura Flap products have a lifetime warranty against defects in materials and workmanship under standard regular use. Damage caused by not using the product as intended, improper installation, and chewing is not covered under this warranty.
- Reviews
- Questions
Finally! One that fits.
A lot of pet panels on the market for sliding glass doors/windows are way too tall for my double wide, but this custom one fit perfectly and the video on the website showing me how to install it made it so easy to put in.

Awesome-ness
This door is a thing of beauty and class. I love it! It fits nicely in my window. Theres no extra noise. There is no outside elements coming in. I would buy this again in a heartbeat. Two thumbs up endura flap!!
amazing
This door was so well worth the money spent. It is so insulating and efficient. I have my air conditioning on and it does not escape through the door. The outside air does not come in either. It was built to fit my window perfectly. I am so impressed with this quality of the door. My dogs are so happy!!1
Perfect product..
My windows open side to side and no one makes a window for cats that goes side to side except for Endura. It is everything I wanted. It is dual pane, stylish, sturdy, energy efficient ect. The flap is staying shut with the weather and the wind. I could not ask for anything better.