Overview

A knob is a rounded handle or protruding control that is operated by turning, twisting, pressing or pulling. Knobs appear on doors, cabinets, appliances, instruments and machines. They serve two basic purposes: as a mechanical interface to move or latch parts, and as a control interface to adjust settings such as volume, temperature or light level. In informal use, "knob" can refer to any small rounded projection.

Common types and examples

  • Doorknob — a round or spherical handle that is turned to retract a latch and open a door; see general hardware descriptions like a doorknob.
  • Cabinet knob — a small grip fixed to a door or drawer front and pulled to open; typically shown on a cabinet door or a drawer.
  • Control knob — a rotary or press control on devices to change settings, for example a lamp dimmer or a radio volume control.
  • Specialized knobs — tuning knobs, potentiometer knobs, instrument controls and decorative knobs used in furniture or appliances; simple protrusions also act as stops or adjustment points such as a drawer catch.

Materials, shapes and ergonomics

Knobs are made from metal, wood, ceramic, glass, plastic or composite materials. Shapes vary from spherical and cylindrical to fluted, faceted or ergonomic contours. Diameter, texture and mounting affect grip and ease of use, important for people with limited hand strength. Designers may add knurling, scallops or detents to improve tactile feedback and repeatable positioning.

Manufacture, installation and maintenance

Typical installation uses a spindle and fastening screw or threaded post; some knobs are push-fit. Maintenance is usually simple: tighten screws, lubricate latch components, clean finishes and replace worn parts. For mechanical or electrical controls, periodic inspection ensures reliable operation and safety.

Control knobs in electronics and instruments

In electronics, knobs attach to shafts of potentiometers, switches or rotary encoders. Their size and shape influence precision and speed of adjustment. Designs often include markings or scales to indicate position; detented knobs provide discrete steps, while smooth shafts allow continuous variation.

Accessibility, standards and selection

Knobs are often compared with levers: levers can be easier to operate for users with reduced grip strength because they require less twisting. For that reason many building codes and accessibility guidelines recommend lever handles on doors in public buildings. Selecting a knob considers function, aesthetics, durability, finish and compatibility with locks, latches or electronic controls.

History and cultural notes

Simple knobs have existed for centuries on chests, furniture and doors. The industrial era expanded their forms and materials, and the electrical age added rotary controls for appliances and instruments. Today knobs remain both functional hardware and decorative elements in architecture and product design.