My Delta Bot needs a "knee". that's the joint between the driving motor, and the "ankle", which is the lower leg of the two legs of the delta bot.This thing is a simple "knee". It has a notch in it so it can be easily connected to other things that have the matching "key".You simply slip a piece of smooth rod, or dowel, or whatever you have that can rotate within the hole, put some bar ends on the axle (like a Clevis joint), and you've now go a knee!UPDATE: 30012011 Added the _half version of the disc axle. The full one is hard to print as a single piece, depending on the quality and type of support/raft your printer has. The 'half' version allows you to print it flat. Just print two of them, and put their flat sides together. You can glue together, or just let the piece that has the key hold them together, depending on your needs.1) Look at your Delta Bot pieces laying in the corner 2) Print 3 of these out 3) Print out some clevis joints 4) Put an axle through the center hole 5) Slip the elbow end of the Clevis Joint onto the axle. 6) Slip rods into the end of the Clevis Joint 7) Connect those rods to something else 8) Rejoice!