Excavators

• Most are mono booms: these have no movement apart from straight up and down.
• Some others have a knuckle boom which can also move left and right in line with the machine.
• The other option is a hinge at the base of the boom allowing it to hydraulically pivot up to 180° independent to the house, however this is generally available only to compact excavators.
Attached to the end of the boom is the stick (or dipper arm). The stick provides the digging force needed to pull the bucket through the ground. The stick length is optional depending whether reach (longer stick) or break-out power (shorter stick) is required.