Abstract: Disclosed are a rotary knob lock, a maintenance tool and an LED display. The rotary knob lock includes a lock body, the lock body includes a head part and a limit part, a diameter of the head part is larger than a diameter of the limit part, the head part is provided with a first magnet, the limit part is provided with a limit block; the maintenance tool includes a body, the body is provided with a second magnet inside, the second magnet and the first magnet of the rotary knob lock are magnetically attracted to each other; the LED display includes an LED display module and a cabinet, the LED display module is provided with a rotary knob lock, the cabinet is provided with an avoidance hole, when the LED display module is mounted on the cabinet, the first magnet and limit block are located on both sides.