https://holmberg-mcgee-3.hubst....ack.net/cat-flap-ins
A through-wall cat flap lets your pets come out and in whenever they like. However, you should be careful not to install it too high in the wall. This can lead to energy loss and the possibility of burglars gaining access to your home. A hole in a cavity can also be a problem for future owners should you decide to sell your home. Glass cat doors offer a safer alternative. Easy to install A cat flap that is built into the wall allows your cat to come and go whenever it wants. It's simple to set up, and there ar