<P> Drum hoists are used for motor - assist, engaging an operating line, and dead - haul, engaging the lift lines, applications . </P> <P> A dead - haul drum hoist uses the single drum to support all the lift lines running from the head block of a line set . The lift lines neatly wrap and unwrap in a side - by - side arrangement on the drum as it is spun by the motor . </P> <P> As a lift line coils and uncoils from the drum of a drum hoist, its fleet angle (angle of a line between drum and sheave) changes . Excessive fleet angles (e.g., greater than 1.5--2.0 °) cause unpredictable line behavior and can damage lines, blocks, and drums . As a result, fleet angles limit how close a dead - haul drum hoist can be mounted to the head block (usually about 10 feet). </P> <P> A moving drum hoist, or traveling drum hoist, is a variation on the traditional drum hoist . Moving drum hoists effectively eliminate the fleet angle between drum and block by shifting the drum along its axis as it spins . The amount of shift per drum revolution is equal to the pitch of the drum's helical groove . With the fleet angle problem resolved, moving drum hoists can combine drum and head block into a single, relatively compact, unit for mounting to fly loft structure, with a corresponding reduction of installation cost . </P>

What is the name of the first rigging level