Yazzo Rod End Bearing

Some times I need a joint.

This thing is one element of a One Degree of Freedom (1DOF?) joint. Put two of these together back to back, and put an axle through their joined holes, and you have a nice joint.

This thing, in conjunction with this other thing: http://www.thingiverse.com/thing:6354 make for an "arm" that attaches to a motor, and can be of any length (based on strength of motor and load).