Learning how to make triangle supports has a whole host of possibilities for creating. The main job of the triangle support is to hold something up, but learning how to make one involves scoring, which is the best way to neatly fold cardboard. Once you can do neat folds, I'm sure you will think of inventive ways to use them.
Start with a long flat piece of cardboard, with the wavy interior lines running perpendicular to the long edge.
Scoring is when you cut through part of the cardboard. Though it is easiest with a blade, kid scissors opened up work pretty well on most cardboard.
To make a triangle, you will need 3 score lines, one for each corner:
Then cut one of the end pieces about an inch away from the last score line.
Lastly, fold on the score lines and glue the flap to the other end.
See video for a step by step!