a hydraulic clamp embedded in a t - slot of a machine tool bolster plate , has a t - slotted piston rod end which fits continuously within the t - slot of the bolster plate . using a t - configured member secured to the underside of a die shoe , and slid into the t - slot , actuating the hydraulic clamp draws the shoe downward , firmly clamping it against the bolster surface . if , instead of a t - configured member , and i - beam member is used in a die shoe having a t - slotted undersurface , the clamping force is extended over the entire length of the i - beam . the effect is to avoid distortion of the die shoe . in addition to the surface friction attendant to the present distortion - free clamping , positive resistance of sideward displacement of the shoe is provided by the t - slot edges . when the present invention is not employed for clamping , the t - slotted surfaces of the bolster plates are unencumbered and may therefore be used and cleaned in an ordinary manner .