A modular, reusable installation tool for clamping laid-together portions of cross-linked, dimensionally heat unstable polymeric material along a to-be-formed bond line during the application of heat from an external source to form a bond between clamped portions of the material. The tool comprises an assembly of hand-operated clip modules which are threaded longitudinally on a cable to facilitate their rapid one-hand installation and removal along a bond line. An improved modular clip is disclosed which incorporates a pair of bond line gripping flanges attached to a pair of ventilated cooperating jaw plates.