Abstract: A hollow horizontal support of inverted U-shaped cross-section has a base plate secured transversely thereto at its rearward end, and also has parallel side walls interconnected by a top wall, and further has a forward end wall with a downwardly-extending portion serving as a fixed article-gripping jaw. Slidably mounted in a hole in this end wall and provided with a movable article-gripping jaw projecting downward therefrom is a spring-pressed plunger, the forward end of which projects forwardly through the forward end wall in a push-button portion, the rearward end of which slidably engages the side wall of a hole in the front wall of a hollow rear spring abutment and plunger guide member of up-ended scoop-shaped form disposed in the interior of the U-shaped support and held therein by integral transverse lugs projecting laterally therefrom and fitting into notches in step portions of the opposite side walls of the support.