Abstract: A cutter for picture frame mats is provided herein. It includes a rectangular cutter base having a planar mat-supporting surface, a hinged frame, a cutter head assembly mounted on a guide rod on the hinged frame, and a stop on the guide frame. The inventive concept is embodied in a novel clamping frame including a pair of spaced-apart, parallel, transverse, lateral hinge bars, each being secured by an associated hinge adjacent its respective rear end. A longitudinally extending handle interconnects the respective forward ends of the transverse lateral hinge bars. A longitudinally extending intermediately transversely positioned cutter head guide bar assembly is disposed between the hinge bars. The cutter head guide bar assembly includes a guide plate having a lower surface which, in use, lies flush with the picture frame mat which is resting on the mat-supporting surface.