Very Simple Machine

I have a couple of lazy kates courtesy of my son and his k'nex set:

You need something to hold the bobbins when you are plying yarn (two 1 ply yarns together make a 2 ply yarn. A real lazy kate usually has something to hold the tension as well. He had tried that last time, but this simpler design really works better. It keeps the bobbins where they belong. I loved how thrilled he was to help me out by making them.