Abstract: A plate for the mounting and supporting of a cutting die to be utilized within a machine for the cutting of envelopes from a stack of sheet paper. The metallic cutting die is held by magnets which are embedded with the plate. Mounted within the plate are a plurality of slidable members which are to engage with the cutting die to fixedly lock the cutting die in the established position upon the plate. Also included within the plate is a breaker bar assembly which can be moved to separate the cutting die from the holding force of the magnets when it is desired to change the cutting die.