See the KREG 90° Corner Clamp in action in the video below:
The KREG 90° Corner Clamp is the simplest solution for holding corner or ‘T’ joints, for examples when making boxes or cabinets. With just one hand, equal pressure is applied to all sides of the corner that is being glued or screwed together. Thanks to the automatic pressure-adjusting system (Automaxx) the pressure applied is never too large to damage the material. The pressure is adjusted automatically to the material thickness.
The shape of the jaws ensures 90 degree joints and edge stops help align the edges of the pieces to make accurate assemblies with one hand.