Ball slides are mechanically simple linear motion devices comprised of a stationary base with a mobile carriage riding on top. One row of hardened steel balls on each side of the base provide the accurate, low-friction sliding motion between the stationary base and the top slide. Each row of bearings is contained between two hardened, precision steel rods. These bearing assemblies are preloaded to eliminate wobble and unwanted play in the system. Ball slides are functionally much more reliable than dovetail slides, since there is no direct sliding contact of top and bottom pieces. Ball slides also eliminate the rapid wear problems, regular lubrication requirements, and the skipping/jumping (caused by the increased force needed to initiate movement) that are characteristic of dovetail assemblies.