Endura Flap Cat Door for Horizontal Sliding Windows

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  • Removable panel with built-in cat door fits into a horizontal sliding window track
  • Durable, aluminum frame and pet door flaps made to withstand extreme weather
  • Made with dual-pane, Low-E glass to improve energy efficiency
  • Tool-free installation
  • Need a different size? Check out this product's custom options

The Endura Flap Cat Door for Horizontal Sliding Windows is made to fit into the existing track of your side-to-side sliding window. It installs tools-free with a spring-loaded design to safely secure into your sliding window track without any permanent alterations (perfect for renters). The removable panel comes with a C-clamp lock, draft stopper and weather stripping. It features dual-pane, Low-E glass that is UV and infrared resistant for maximum insulation value. The flexible flap is lined with adjustable magnets to resist heavy wind and extreme temperatures.

The panels have a 3" spring-loaded height adjustment, so if you have a 48" track, for example, the panel you choose will adjust from 46" - 49" inches. Need a different size? Check out our custom sizing options


  • Aluminum frame designed to fit into a window track width of at least 1" thick
  • Comes with a C-clamp locking option, draft stopper and weather stripping for security and insulation of flap opening
  • Dual-pane, Low-E glass allows natural light to enter while blocking out unwanted UV rays and infrared light
  • Flap withstands -40 degrees
  • Fahrenheit temperatures and stays sealed in 50mph winds
  • Magnetic sealing closure resists heavy winds/storms
  • Flap swings on a rod at the top, avoiding breakage
  • Includes a sturdy locking cover


  • Removable panel benefits all owners, especially renters.
  • Don't need to make any permanent alterations to window
  • Available in white, bronze, or brushed aluminum to match your window frame
  • Locking cover prevents pets from leaving the house when you want to keep them inside
  • Made with durable, long-lasting materials

Size Chart

Flap SizeFlap DimensionStep Over RangeOverall Panel WidthRecommendedPet Height*
Small 6" w x 11" h3" – 5"11 1⁄4"9 – 15"


Track Height Adjustment Range is the measurement of your window height from the lowest point of your track to the highest point. Review our Track Measuring Guide for more information. The Endura Flap Cat Door for Horizontal Sliding Windows comes in two adjustable ranges:

  • 34"-37"
  • 46"-49"


If your measured track height does not fall within one of the ranges above, we can make a custom height. Custom height option may take up to 4 weeks to special order the glass and build the panel. If your measured track height is near the bottom of the adjustment range then you should review A Note of Caution.



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.

Additional Information

Flap Material


Your Maximum Pet Size

Cats, Large Cats

Climate Suitability

Severe-4 Season

Type of Window

Sideways Sliding

Sealing Value

Very High

Wind Resistance

Very High

Installation Instructions


All Panels

  • 1x Foam Weather Strip
  • 1x Center Post Weather Seal Draft Stopper

1 Piece Pet Door

  • 1x Panel Pet Door
  • 1x Sliding Door Clamp

2 Piece Pet Door

  • 1x Top Glass Panel Section
  • 1x Bottom Flap Section
  • 4x Hex screws
  • 1x Hex wrench
  • 1x Threshold mount deadbolt with screws



The aluminum, vertical panel has a patented ‘Adjustable Step-Over’ feature which permits adjusting the height of the flap to the most comfortable fit for your pet. Generally, the top of the flap should be positioned to be at least 1” (2,5 cm) above the top of the pet’s shoulder (the ‘withers’). If the factory setting is not suitable, please adjust it before proceeding. If the current setting is suitable, or you have the vinyl panel, proceed to step 3.



Step 1A: Two-piece panels: 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.

One-piece panels: Lay the entire panel on a flat surface (like the floor). Using a #2 Phillips head screwdriver, remove the bottom side-screws, and loosen the next upper screws one turn. Screws were tightly installed to hold the panel together during shipping; a drill is recommended*.

*If you do not have a Phillips head drill bit skinny enough to fit, let us know and we’ll send you one for free.

Step 2B: One-piece panels: Once the bottom screws have been removed and the next upper side-screws loosened, the Pet Door Assembly and spacers can be removed by sliding the sections down and out of the panel. 

Step 2C: 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.

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. 

When finished, replace the bottom side-screws and tighten the next upper-side screws for one piece panels and skip to step 4. For two-piece panels, you can now assemble the patio panel!

Please Note: A lower step-over height is easier for pets to navigate. However, if the top of the flap is low enough that the pet needs to crouch to get through their pet door, they can injure themselves and possibly cause the pet door to malfunction. If your pet door does not sit at a comfortable height for your pet, you may need a larger size flap. 



(If you have a single piece panel, please proceed to step 4)

Step 3A: 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 & thumb screws are on the same side!

Step 3B: 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 3C: Fasten the two panels together using the four stainless steel hex head screws found in the panel packaging. Use the hex wrench to tighten screws so the two halves of the door are pulled together.

Please Note: Screw holes may look misaligned; this is intentional to ensure a tight fit. The panels will squeeze together as the screws are tightened.

Step 4: Loosen the thumb screws at the top of the pet panel. This allows the spring mechanism to move freely up and down.

Step 5: To insert the panel pet door 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. If you can’t quite get it in the track, try swinging in from the outside as the outside track wall may be shorter.

You want to put the pet door in your track before applying any weather-stripping to ensure it fits! If it fits well, move on to the next step. See our tips at the end of these steps if you have trouble!

Step 6: Once you’re sure the panel fits, remove the panel 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 to fit with scissors. 

Step 7: The center post weather seal strip (draft stopper) should be installed on the inside of the home. It can install on either the back edge of the sliding door panel or the leading edge of the stationary panel. This strip prevents air leaking between the sliding glass door and the stationary panel. Trim with scissors as needed. Clean the edge of your patio door with rubbing alcohol before installing to assure a good seal.




How to Adjust the Magnet Strength on an Endura Flap


How easy is this to install?

The spring loaded design makes installation of the cat door panel very easy. No tools are needed, you simply hand loosen the screws pop the door in the track and re-tighten them. Once it is in place you can't remove it from the outside either, so it's safe and secure.

How do I measure to make sure that it fits?

You will need to open the window and measure from the deepest down inside the bottom of the track and all the way up into the track at the top. You will also need to measure how wide the track is, since the panel is 1" thick your track has to have at least that width to be able to accommodate it.

What do I do if none of these door sizes will fit my window?

If none of the size options will work with your window, you can get a custom cat door.

How strong is the seal on the pet door flap?

The magnets are stronger than your typical off the shelf pet door, so they will have to push the flap a bit harder to get it open. You can adjust the magnets in the beginning for training purposes by reducing their strengths, however you will lose some of the sealing power.

Is this just for cats?

Small dogs can also use the flap, as long as they can comfortably make it through a 6"w by 11"h opening.

Does this keep out drafts?

This panel has dual pane insulated glass and the flap seals extremely well so it is great if you are looking for energy efficiency.