Hot melt adhesives, also called thermoplastic adhesives, are basically blocks of thermoplastic adhesive material that can be melted at very high temperatures and applied to a component. When a hot melt dries, it has adhered to the component in much the same way as glue. In fact, hot glue guns use a type of hot melt adhesive.

Typically, there are two main systems through which a hot melt adhesive is applied: melt-reservoir systems and pressure feed systems.

Reservoir systems can handle a large amount of adhesive, which begins in a heated reservoir holding area. After being pumped through a feed-hose, the adhesive is either applied via an extrusion gun or wheel, which deposits a layer of adhesive on the specific component. These types of systems are appropriate for low-performance adhesives, and can deposit about 4 to 5 kilograms (kg) of adhesive per hour.

Progressive feed systems are suited to handle a much smaller amount of adhesive. In industrial variants, adhesive pellets are transferred from a hopper to a heated grid, where they melt. Next, the heated adhesive is fed though a pump, pressurized, and then fed through a hose into a heated gun. Around 9 kg per hour, but keeps a very small amount in a melted state at any given time. For non-industrial systems, hand-held glue guns serve as a much smaller type of progressive feed system.