Knob
From Wikipedia, a free encyclopedia written in simple English for easy reading.

Control knobs to change the hot and warm air in a hotel room.
A knob is a round handle you turn or pull. A doorknob is a round handle you turn to open a door. A cabinet knob is a small handle you pull to open a cabinet door or drawer. A control knob may turn a lamp on and off or make the volume on a radio go up or down.
A knob can also be any small, round thing that sticks out.