Special Features:

Concentric knobs, attached by center screw

Properties:

An item designed to transmit manual, rotary or linear motion to other devices. May include detachable or nondetachable stud (shaft), pointer, or skirt. It may have reference markings in the form of dots, arrows, hairlines, and/or symbols which may be used in conjunction with a calibrated panel, vernier indicator, and the like to indicate the position or motion of items. For items having spokes or simulated spokes radiating from near the center to near the outside rim of the item and relatively thin round disk-shaped items 3 inches (76.2 mm) in diameter or over, see handwheel. For items calibrated in units or series of divisions to denote relative positioning of devices see dial, control. Excludes doorknob; and handle (as modified).