A manual slack adjuster is a mechanical device

A manual slack adjuster is a mechanical device that is used to adjust the tension on the brake shoes of a drum brake system. It is a lever that is attached to the brake shoe and extends through a hole in the brake drum. The other end of the lever is attached to a mechanism called a pushrod, which is connected to the brake pedal or the brake master cylinder. When the brake pedal is pressed, the pushrod pushes on the manual slack adjuster, which in turn pushes on the brake shoe and applies the brake. The slack adjuster is used to maintain the correct tension on the brake shoes and ensure that the brakes function properly. It is typically adjusted by turning a nut or bolt on the end of the lever.
chinafuao.net