I used to make these out of wood on a bandsaw in my high school wood shop about 45 years ago, albeit much larger than this version. My shop teacher would measure the finished cube to make sure it was exactly 4" by 4" by 4" (oh the good old days when teachers expected finite results). This 3D printed version is much easier to make, and is only 40mm by 40mm by 40.2mm (.2mm too tall, hope he doesn't notice). And it does not require hand cranking, motors, glue, etc., well not yet at least... Video at http://www.youtube.com/watch?v=mEr1gaCMv5g&list=UUv_zm49u-RjnCJVwhUO-ecA&feature=c4-overview. Designed using Sketchup 8, and printed in PLA on a Makerbot Replicator 2 in PLA using Makerware 2.3.3.42. UPDATE: I've added the tall versions of the two pieces as requested by a few of my fellow 3D printers. Just print the two pieces in the colors of your choice and slide the them together.