Abstract: An improved clamp for releasably and adjustably securing accessories, such as hanger rods for parenteral solution containers, to medical tables. The clamp has a generally cylindrical body comprising two main sections arranged in axial alignment: a base section and a cup section. Annular rows of intermeshing teeth are provided along the opposing end faces of the respective sections to prevent relative rotation of those sections unless such movement is accompanied by slight axial separation. The cup section includes a chamber terminating in an enlarged end opening that rotatably receives the cylindrical shank of a first operating knob. The knob is threadedly supported upon a hollow stem which is joined at one end to the base section and which extends axially through the chamber of the cup section.