An adjustment mechanism for a lifting device, the adjustment mechanism comprising: a. a longitudinal clamp bar ; and b. a clamp slidably disposed on the clamp bar , the clamp comprising: i. a clamp body; and ii. at least one clamping member movably connected to the clamp body, the at least one clamping member being operative for: - acquiring a clamped condition when a lifting force is applied to the clamp body, wherein in the clamped condition, the at least one clamping member is engaged with the longitudinal clamp bar to prevent movement of the clamp along the clamp bar ; and - acquiring an unclamped condition when a lifting force is released from the clamp body, wherein in the unclamped condition, the clamp is free to move along the clamp bar ; characterized in that the clamp body comprises an upper clamp element and a lower clamp element movable in relation to each other, wherein the upper clamp element connects to the lower clamp element via the at least one clamping member; in that the upper clamp element comprises two slots and the at least one clamping member comprises four pawls ; and in that a first shaft is slidably disposed in each slot , connecting upper ends of two of the pawls together on opposite sides of the upper clamp element . a. a longitudinal clamp bar ; and b. a clamp slidably disposed on the clamp bar , the clamp comprising: i. a clamp body; and ii. at least one clamping member movably connected to the clamp body, the at least one clamping member being operative for: - acquiring a clamped condition when a lifting force is applied to the clamp body, wherein in the clamped condition, the at least one clamping member is engaged with the longitudinal clamp bar to prevent movement of the clamp along the clamp bar ; and - acquiring an unclamped condition when a lifting force is released from the clamp body, wherein in the unclamped condition, the clamp is free to move along the clamp bar ; i. a clamp body; and ii. at least one clamping member movably connected to the clamp body, the at least one clamping member being operative for: - acquiring a clamped condition when a lifting force is applied to the clamp body, wherein in the clamped condition, the at least one clamping member is engaged with the longitudinal clamp bar to prevent movement of the clamp along the clamp bar ; and - acquiring an unclamped condition when a lifting force is released from the clamp body, wherein in the unclamped condition, the clamp is free to move along the clamp bar ; - acquiring a clamped condition when a lifting force is applied to the clamp body, wherein in the clamped condition, the at least one clamping member is engaged with the longitudinal clamp bar to prevent movement of the clamp along the clamp bar ; and - acquiring an unclamped condition when a lifting force is released from the clamp body, wherein in the unclamped condition, the clamp is free to move along the clamp bar ; characterized in that the clamp body comprises an upper clamp element and a lower clamp element movable in relation to each other, wherein the upper clamp element connects to the lower clamp element via the at least one clamping member; in that the upper clamp element comprises two slots and the at least one clamping member comprises four pawls ; and in that a first shaft is slidably disposed in each slot , connecting upper ends of two of the pawls together on opposite sides of the upper clamp element . <EOS>