The wire from the smart cat flap kept getting caught by the door. A simple problem, with a simple solution.
There are commercial door loops readily available, but why buy new when you have a shed full of parts? The loop is made from approximately 30 cm shower hose. Cutting it with a hacksaw is tricky because of the interlocking metal wrap. I would use an angle grinder next time. Be sure to file and sand the edges, you don't want the edges to cut into the wiring. The loop is held in place with electrical conduit clamps.
The result is not the most beautiful thing, but it's practical, free and made quicker than a round trip to the hardware store.