Round self-locking washers are used to secure insulation material on insulation pins that have been welded or stud-welded to the insulated surface. The selection of washer size and material (e.g., galvanized steel or stainless steel) depends on the operating temperature of the insulated system, the insulation thickness, and other specific technical requirements.

The washers hold the insulation material in place on the pins, preventing displacement. They are most commonly used for installing rock wool wired mats on ducts, tanks, and similar equipment with flat or inclined walls.