Abstract: A foam board insulation shaping system and method for hot wire shaping insulation board to fit roof contours, wherein a frame mounts a transversely disposed, generally horizontal, linear wire and conveying rolls move the foam board along a longitudinal pathway past the wire, which melts the plastic as the board moves. Wire clamps secure the ends of the wire and are mounted for vertical movement, one of the wire clamps being also mounted for transverse movement relative to the frame. Yieldable mechanism associated with one of the clamps provides for expansion of the wire linearly with heating, while maintaining it under tension. A motor drives the clamps to move them vertically in unison at a predetermined speed with relation to the speed of the board. A series of transversely spaced, generally U-shaped hot wires are provided for forming grooves in the upper surface of boards, and means are provided for electrically energizing the linear wire and the U-shaped wires.