https://www.openlearning.com/u..../scottkelley-smalv4/
Cats are fond of looking out of windows, which is a form of entertainment sometimes known as cat television. It's a natural and entertaining pursuit that is often hunter-like. You can fit glass window inserts that have cat flaps to existing doors or windows. They can also be fitted to double glazing. Easy to Fit Cat flaps are fitted in most types of glass windows and doors that have double glazing, single glazing, french doors and patio doors, bifold doors, and leaded units. They are great for people who