In our study of simple machines, we take a look at types of levers and situations where the torques applied to them are equal allowing objects to be balanced. Here is a simple set of blocks that can be used to challenge student's understanding and their manipulation skills by having them attempt to stack levers on top of levers. Made with simple scraps of wood, it does take a bit of skill to use up all of the block in this building effort. The levers are built upwards, sort of the reverse of the mobiles that can hang from the ceiling. The basic explanation of torques and how why levers balance are explained in the previous video on mobiles. Whether the levers are hanging down from the ceiling or being build up from the desk, the basic concepts are the same.