The Girl Cat, bless her, now has four of what they call Cat Flaps and two of those Cat Flaps are on either end of a private foyer attached to the domicile that's large enough to accommodate one medium sized snoozing cat, The foyer has two very small windows that catch the morning sun and it can get quite sleep making in there. The more sane may not have a clue what a Cat Flap might be. And I'd agree the name Cat Flap does suggest some sort of feline mental breakdown followed by rushing around looking for a paper bag to hide in. So let me attempt an explanation of the nature and function of a Cat Flap to the less obscurely preoccupied and much more sensible members of my own species.
Picture something like a domicile, doors, windows roofs, insulation and whole
set of arrangements designed primarily to keep out the unwanted, especially
things like straight line winds containing snow and ice, as well as things like
Marmots, Groundhogs, Raccoons, Squirrels, little boys and the list is a very
long one. Then cut a nice rectangular hole in this secure and well considered
structure and install a flap large enough for a small, elegant Cat, or any
number of alternatives, to push open whenever the mood takes her or them. For
those still mystified, flaps are designed to flap, they don't have door handles
or latches because Cat's don't have opposable thumbs. A more interesting
question is perhaps whether being Cat Flap Rich defines a person's tribal
allegiances? I say Yes to this question.