There are two types of coal tar used in roofing. Type III is called coal tar bitumen. Both work well, but Type III does not give off as much coal tar fume as Type 1. Both kinds of bitumen are heated in kettles or tankers. Kettles are trailers that get towed by trucks.
Tankers are trucks that can be driven to a job site.
Both are large heating tanks for melting bitumen. The material is usually pumped up to a roof through a sup-ply line. It is important that bitumen is kept at the right temperature in the kettle. If it is overheated, its quality will not be as good. Overheated bitumen can also catch fire.