Designed For Installing Rear Window Glass in Vehicular Cabs, Coaches, Trailers, and BoatsThere are two simple steps to install rear window glass in vehicular cabs, coaches, trailers and boats. 1. Insert one of the spreader hooks into the solid channel spreader handle. Tighten set screw with allen wrench. Use the channel spreader to open the glass channel of the weatherstrip, allowing the glass to seat into position.