A tool is provided for applying adhesive material to a surface. The tool utilizes a cartridge of heat-softenable, thermoplastic material which is positioned in a chamber of the tool. Air under pressure at the rear end of the chamber is applied directly to the rear of the cartridge to urge it toward a heat block located at the forward end of the chamber. That portion of the adhesive material in contact with and near the heat block is softened and flows through passages in the block and past a check valve to a nozzle from which the softened adhesive is directed to the surface. The heat block has a plurality of radially-extending fins which are designed to concentrate heat at the center of the cartridge. The tool features a sleeve of plastic material in the cartridge chamber adjacent the heat block, which sleeve is isolated from the rear portion of the chamber to minimize the conduction of heat toward the rear. The chamber also has three annular, resilient seals therein which separate the air applied to the rear of the cartridge from the forward portion of the chamber with the rear seal also serving as a guide to maintain the adhesive cartridge in proper alignment in the chamber. The chamber has a vent located between the forward two seals through which air passes when the rear end of the cartridge is moved forwardly between these two seals. This serves as a warning to the operator to insert a new cartridge. The new adhesive tool also is equipped with improved heat controls.