A unit is a piece of machinery or equipment that has been divided into separate units to provide a single function. Unit parts play a role to create these units. The advantage of a unit is that the machine or equipment is completed by simply attaching the completed unit to the machine or equipment, which leads to effective use of assembly space and reduced time for maintenance. Also, in many cases, when parts are ordered in units, work cannot start until all the parts are available. However, by ordering units, they do not need to wait until all the parts arrive.