Calling all pragmatists: how to construct a regular pentagon without even a compass?

Start with a ribbon of paper. (How you construct that is a separate problem.)

Fold it into a simple overhand knot. Gently pull tight and flatten. The knot is a regular pentagon. !

(Q: What does "pragmatist" mean?
A: I don't know, but it doesn't really matter as long as I can use it properly.)