Heat sealers fuse together two bits of material, with at least one thermoplastic layer. A controlled heating element heats the plastic, and upon cooling, the seal forms. These machines are ideal for packaging foods that do not require an elimination of air, but a more controlled atmosphere. Tray sealers, or overwrappers, are great for butcher shops and retail food outlets who need to pack on the go. Film is wrapped over the product, usually in a tray, and sealed using a heat pad. The result is a neatly packed product with a fresh appearance that looks great in the display cabinet.