At the weekend I bought a new cat flap for Mrs Botogol (no, don't be silly, of course not: for her cats)
Now, when it comes to fitting cat flaps I actually have form. I don't want to rake over old domestics, so I'll just mention a new cat-flap, a stupid glass cutter where you simply scratch a circle and then (supposedly) sharply tap once and remove the glass, and an emergency glazier. On Boxing Day.
So this time I read the instructions very carefully.
First, measure the belly-height of your cat.
"KIDS!", I yelled, "I've got a job for you" and went off to fetch the muzzle.