Abstract: A height adjustable mechanism for supporting a work surface for vertical movement relative to a base includes a counterbalance mechanism for providing a force opposing a downward force tending to lower the work surface; a brake mechanism for releasably retaining the work surface in a desired vertical position; a user operated release mechanism for selectively releasing the brake mechanism to permit vertical movement of the work surface; and an interlock mechanism for preventing release of the brake mechanism if the force and the downward force are out of balance by some given extent.

Abstract: A mechanism for supporting an auxiliary surface for vertical movement relative to a primary surface includes a pair of link elements having opposite ends pivotally connected to auxiliary and primary surface mounting elements or brackets, a first bias for opposing downwardly directed swinging movement of the link elements relative to the primary surface mounting element, a second bias for opposing pivotal downwardly directed movement of the auxiliary surface mounting element relative to the link elements, and a locking mechanism for releasably constraining swinging movement of the link elements and pivotal movement of the auxiliary surface mounting element. The locking mechanism features a roller and an operator arranged to engage with the roller when moved into a locking position to effect clamping together of the link elements and the auxiliary surface supporting element.