Checking slack adjuster movement takes the guesswork out of the adjustment. It's a one man operation.

By hooking the end of the tool onto the manual slack adjuster and pull. If the brakes are properly adjusted, free play should not exceed 1".

If there is a need to free-up the locking collar, use the hammer part of the tool.

If an adjustment is required, use the opposite 9/16" end of the tool to turn the adjusting hex nut.

What could be easier?