The most common grease gun is the hand-lever style for its economical price. This type can be more difficult to operate however, because the aperture on the tip of the hose on the grease gun sometimes requires pressure applied (by hand) to the zerk fitting in order to properly pump grease into the fitting. The hand-lever style requires one hand to hold the chamber of the gun steady while pumping the lever with the other hand, leaving no hands to apply pressure to the aperture. A finger-trigger or hand-trigger type grease gun is a better alternative because you can hold the gun and then squeeze the trigger with the same hand while using your opposite hand to apply the necessary pressure to the aperture on the zerk fitting
Another less popular style grease gun uses a manually pressurized chamber without a trigger or lever apparatus. The placement of the aperture onto the zerk fitting releases the pressure and purges grease into the fitting.
Some grease guns use pneumatic pressure instead of the manual spring-loaded plunger. This type is found in shops that use air compressors for their equipment where a lot of grease is used. Often times, the grease provided to the guns is stored in large barrels and the air compressors apply the pressure from a pump placed at the top of the barrel, through a pneumatic hose and into the gun. Pulling the trigger of this style gun will continuously pump grease from the aperture until the trigger is released.
