method and apparatus for trimming plastic frames . frames are joined to bring heated , soften ends into engagement , causing some softened material to be forced out from between the engaged portions , forming a flashing . this flashing is trimmed by a pair of trimming blades moved along associated guide members . the trimming assembly is mounted directly upon clamps holding the frame members , enabling performance of the trimming operation and eliminating the need for moving to a separate trimming / finishing station remote from the joining equipment . excellent cutting action is assured by locking the guide blocks preparatory to a trimming operation . various combinations and sequences of repetitive trimming operations may be selected whereby the cooperating blades are moved in selective cooperating directions to provide a trimming operation which avoids the need for further finishing . trimming may also be performed simultaneously on multiple stacks of members being joined using the above technique .