The entire assembly of the heddle and its frame is the heddle shaft or wire harness. When the weaver lifts the wire harness, the warp yarns controlled by the healds rise to form a shed or open space for the weft yarns to pass through.

Among the two types of healds: suspended and rigid healds, the easiest to learn is generally the rigid healds. This is just a piece of wood or plastic with alternating slots and holes.

The healds are made of various materials. Which material a weaver uses to make healds is mainly a personal preference. Some weavers believe that the thread is more gentle on the warp. Others find that flat steel is stronger and less likely to break.

The heald is a device that controls the warp or longitudinal threads during the weaving process. When weaving on the simplest loom, one person manually manipulates the weft or cross threads above and below the warp threads. On more complex looms, healds control the warp.