Slack adjusters are mechanical devices that are installed on a heavy goods vehicle (HGV) to adjust and maintain the proper tension on the brake shoes or brake pads of the brake system. They are typically found on the brake drums or brake rotors of the vehicle's wheels. The slack adjuster connects to the brake actuator, typically an S-cam or a brake chamber, and when the brake pedal is depressed, the brake actuator pushes the brake shoes or brake pads against the brake drum or rotor, creating the braking force. The slack adjuster is responsible for keeping the brake shoes or brake pads in the correct position to maintain proper contact with the brake drum or rotor. As the brake shoes or brake pads wear down, the slack adjuster needs to be adjusted to maintain the correct tension. This is done by turning the adjustment screw on the slack adjuster until the correct tension is achieved. Slack adjusters are important for the proper operation of the HGV brake system. They are responsible for maintaining the proper tension on the brake shoes or brake pads, which ensures that the brakes are working effectively and safely. They should be inspected and adjusted regularly, as recommended by the vehicle manufacturer, to ensure that the brakes are working properly and that the vehicle is safe to operate.