An adjustable clamp for maintaining two butting panels in an adjoining relationship. A clamping base is composed of a pair of base plates connected at each end with a scissor hinge allowing the plates to be secured at angles of from 0° to greater than 90° to one another. Clamp members are provided on each of the base plates for clamping panels in the desired butting relationship for gluing or otherwise joining the butting panels along their butting edges.