Pet cats don’t keep regular hours, but you don’t have to be at the beck and call of yours — if you install a cat flap. A specialized pet door for your feline to come and go at will means that they can let themselves in and out without you having to wake up at odd hours, or even when you are not at home. Weatherproofing the entrance and being sure it is the right size are important factors, as well as placement of the entry.
Remove the door the cat flap will be built in. You will need a wooden door to install a cat flap. You can find pre-fabricated pet doors designed to fit metal frames.
Measure the inside dimension of the opening. Cut four pieces of the 1/2 inch board to fit the inside of the square. Cut the two top and bottom pieces to match the dimension of the inside of the square, and cut the two side pieces one inch smaller, to make room for the top and bottom pieces.
Cut eight pieces of 1-by-1-inch trim, to the size of the outside dimension of the opening. Glue and screw them in place on both sides of the door to conceal the seams around the cat flap opening, and cover the hinges where they are hung on the door.