Two large tin cans (food), cord or string.

The empty cans need to be quite strong and large, i find pineapple chunks particularly suitable. The tins should be opened by the type of tin opener that doesn't leave a sharp edge. Using a bradawl get your guardian to put a hole in each side of the can. The holes should be at the bottom (Non opened) end of the can. Measure the length of your legs then double that and cut 2 pieces to this size. Thread the cord through the holes in the can and tie the two ends together. If you are clever you can tie the knot so that it is hidden in the centre of the can.