Agile Tetrahedron Model I was in a workshop just the other day and asked if everyone was aware of the dynamics of the classic project management iron triangle. While most people had heard of it, it was apparent that few actually understood the dynamics of the model. For a better model than the PM triangle see the Agile Tetrahedron. Perhaps a physical model of the PM triangle would help people to grasp the meaning. So let's build an adjustable Iron Triangle out of something. It needs to be inexpensive, made from common items, and build-able in 20 minutes. Here's is how to make a PM iron triangle out of plastic drinking straws. You need: Straws - the bendable kind - multi-colored. Scissors I used 3 yellow straws for the flexible corner pieces. Cutting the straw just about 2cm beyond the flex on each side. I cut the straw at an angle. This makes assemble easier, as you must crimp and slide this piece into other straws. The taper makes this easier.