I have a strip of paper with parallel sides, a pencil and a straight edge.
How can I construct a regular pentagram (star) with these? And for that matter, a pentagon? Well ... the pentagon is the proper way to go.

Tie a simple ‘knot’ in the paper, as if was a piece of string; ie, form a loop and pass one end through it. Carefully tighten and flatten the ‘knot’. The shape will form a regular pentagon. Plot the vertices from this template. It is only now necessary to join the vertices to construct the pentagram, or the pentagon. Depending upon the thickness of the paper, you can see an almost complete pentagram if you hold it up to the light.