Abstract: A versatile user-adjustable clamp for clamping accessories to the panels of ready-to-assemble furniture articles, and other surfaces such as countertops, has a main body member, a jaw member, and a knob. The main body member has a substantially spool-shaped section with accessory interface means at opposing ends thereof, and a rectangular section that projects tangentially from the spool-shaped section. The spool-shaped section of the main body member telescopingly receives the jaw member, and has a knob-receiving aperture. The knob is rotatably secured within the knob aperture and provides a means for actuating the telescopic movement of the jaw member relative to the main clamp body. The jaw member includes a flat surface interface that is oriented parallel to the rectangular section of the main clamp body, and has a separate accessory interface means therein.