1.) Remove pet door from door (or wall).

2.) Use side cutters to cut away top portion of one side. (Cut 2" in and 2" down. On Mag II door make the cuts 3".)

3.) Slide flap out to one side and remove hinge pins (by tapping outwards with hammer), carefully so as not to bend them.

4.) Lay new flap into frame lining up hinge pin holes on flap with frame and tap hinge pins back in.

5.) Remount pet door.