Back to the lift tables for a brief moment, here we can see the mechanism by which they do their magic. Centered under the table is a 3 ton bottle jack, operated with the lever the extends to the table edge. This jack is the only hydraulic part of the mechanism, lifting and lowering the tabletop, while the load is stabilized by the four pistons at the corners. The large, four inch diameter sleeve contains three machined nylon "doughnuts" that keep the two inch steel tubing aligned. Since hydraulic jacks are not designed for, or safe for, supporting weight, the two inch tubing is drilled at intervals for pins that hold the full weight of the table at rest. So, the table is jacked up, pins are set, and then the jack is released so that the table is safe to work on, around, and under. Voila.