Abstract: A cutting guide assembly consists of a pair of guide rails in end-to-end abutting relationship with a clamping plate frictionally engaging each guide rail to secure the rails together. Each guide rail has a cross section defining a channel. A ramped or inclined lip is disposed within the channel, and is engaged by the end of a flange provided on the clamping plate to force the flange toward an inwardly facing stop surface defined by a wall of the guide rails. A series of set screws provide relative downward movement of the clamping plate, to cause the end of the flange to ride on the inclined surface and to force an outwardly facing surface of the flange against the stop surfaces of the guide rails. In this manner, the vertical guide surfaces of the guide rails are automatically aligned with each other when the rails are secured together. The clamping plate includes a second flange, which engages a supporting surface formed on a second inwardly extending lip.