Brodie knob

Some heavy automobiles without a power steering system tended to have heavy and slow responses requiring hand-over-hand turning of the wheel by the driver, and the knob allowed the driver to "crank" the steering wheel to make faster turns.

They are also used on forklifts, farm tractors, construction equipment, riding lawnmowers, and ice resurfacers, where frequent sharp turning is required.

[3] The knobs are sometimes installed as an aftermarket accessory on farm and commercial tractors, their primary purpose being to ease one-handed steering.

If the driver is wearing a long-sleeved shirt, the protruding accessory on the steering wheel's rim can also become caught in the sleeve's open cut by the button.

The U.S. Occupational Safety and Health Administration (OSHA) regulations restrict the use of auxiliary devices for specific construction vehicles.