Apparatus for clamping a device to a work surface. A cam actuated, adjustable clamp provides a connection between the device and the work surface. The clamp includes a handle and a lever pivotally coupled to a housing member; a hand rotated threaded bolt in the end of the lever is used to adjust the position of a shoe to accommodate work surfaces of different thicknesses. The handle and lever pivot about bearings on two rods. Connectors extend between the two rods and they are coupled to the housing member. Cams on the handle ride on a surface of the lever as the handle is moved, applying a force to the lever that controls its position relative the underside of the work surface. The clamp is engaged/disengaged by a single movement (approximately 90 degrees of rotation) of the handle. A spring or linkage may be provided to bias the lever away from the work surface when the clamp is in the open (disengaged) position.