Ball splines are specialty linear bearings that combine nearly frictionless axial motion with highly constrained rotational positioning. They consist of a grooved nut that moves up and down a central shaft with matching grooves. Balls run in these splines to enable nearly frictionless axial motion. At the same time, the shape of the grooves and the shaft are such that the nut is rotationally fixed so that it can stabilize the load and/or transmit torque. Ball splines are particularly well-suited to applications with overhung or moment loads.