A clamp that comprises a clamp column extending upwardly from one end of a base. The clamp column has a first clamping plate at its free end. An adjustment column also extends upwardly from the base and is spaced parallel to the clamp column. The adjustment column includes a threaded section on its free end. A clamp arm is disposed in spaced parallel relationship with the base and the clamp arm includes a second clamping plate in alignment with the first clamping plate. An opening formed through the clamp arm is positioned in alignment with the adjustment column. A shaft that has a lower threaded section extends through the opening in the clamp arm to threadably engage the threaded section of the adjustment column. The shaft is selectively rotated to adjust the spacing between the first and second clamp plates. An over center cam lever has one end element pivotally attached to the top section of the extending above the clamp arm shaft and a second end element forming the hand grip. A cam lobe on the one end element contacts the clamp arm and the lever is movable between a clamping position where the cam lobe exerts clamping force on the clamping arm and a release position where the cam lobe releases the clamping force on the clamping arm.