Sometimes if the channel width of your doors is too narrow the top adjustable piece won't fit. This can be fixed, it requires cutting the top piece of your pet door.
Warning! The following will void your warranty. You do so at your own risk. Always use proper safety precautions and PPE when modifying your pet door. Consult a professional if you are unsure.
#1 To cut the top piece of your door first measure the depth of your tracks. This length will determine how much you need to cut off your top piece.
#2 Pull the top piece all the way out of your Patio Pet Door.
#3 Remove the top piece from the support bars by removing all the screws.
#4 Measure your track depth on your doors onto the side of the top piece and mark the distance. Draw a line from top to bottom of the top piece. This will be your cutting line.
#5 Cut the top piece along the line you have drawn.
#6 After your top piece has cooled, reattach it to the support bars and put it back into the pet door.
#7 Your Patio Pet Door should now fit!