Manual epoxy glue guns are operated by applying pressure to the trigger, similar to a caulk gun. They don't use electricity and don't require batteries. If you're applying epoxy for many hours, squeezing that trigger can get tiring. It's also not the most precise way to dispense epoxy. Pneumatic epoxy guns attach to an air compressor for assistance, providing more comfort and more precise dispensing. They are commonly used in product assembly, including automotive assembly, where large amounts of epoxy are used.