I like this curtain.

This curtain hangs precariously from little crocodile clips, which hang from a rather unsubstantial wire above our door from the porch (or to be precise...airlock). It's there to keep the draft, caused by the cat flap, out. It's a temporary measure.

I bought two of these beautiful, lined and long enough for Edinburgh georgian windows, from a charity shop about 8 years ago for....wait for it......£2!!!!!