https://stairways.wiki/wiki/Fitting_a_Cat_Flap
Professional cat flap installers will install your pet's door into either a door, or a wall. This is more secure as the burglar cannot reach through it. It also reduces energy costs and prevents draughts. The Tasker will mark where the cat flap is inside your door, and then drill the corners. They will also sand the edges of your frame to give it a smooth finish. Microchip cat flaps A microchip cat flap is a simple and effective method to keep your pet inside your home. It reads the unique microchip identification in the collar of your pet