Knob

A knob is a rounded control or projection used to grip, turn, or pull, and is commonly found on doors, furniture, appliances, and instruments. Knobs are distinct from levers and handles in that they are rotated or pressed rather than primarily pulled or lifted. They can be decorative as well as functional, and may be made from metal, plastic, wood, or ceramic.

Door knobs are hardware components that operate a latch or bolt to secure a door. They are usually mounted on a spindle that connects paired knobs on either side of the door, or on a single knob with a latch. Depending on the function, door knobs may be privacy (bedroom/bathroom), passage (hall/closet), or dummy (non-operating) on one side. The knob and latch mechanism may be surfaced with a rosette, plate, or escutcheon and come in various finishes. Common materials include brass and stainless steel, along with zinc alloys and plastics. Knobs may be keyed for entry or non-keyed and are typically designed to meet building code requirements.

Control knobs encompass the front-panel knobs used on household appliances, audio equipment, and electronic devices. They typically rotate to adjust settings or select functions and may be push-pull or momentary as well. The shaft attached to the knob drives a potentiometer, switch, or electronic control. Front-panel knobs often feature indicator marks, knurling, or textured grips to aid rotation.

Other applications include furniture knobs for drawers and cabinets, which are chiefly decorative or ergonomic handles, and guitar knobs used to control volume and tone on electric guitars or basses.

In design and accessibility contexts, knob size, grip texture, and turning resistance affect usability, especially for people with limited hand strength. Levers are sometimes preferred for accessibility because they are easier to operate with a closed fist.