It's just the same as a limit.

Run 24V to the Input (+) then run Wire from PSU (0v) to the Crocodile clip and return the wire on the plate back to the Input (-)

Or if you want to do away with the Crocodile clip run a wire from the 0v to the Spindle mount or Chassis if the spindle is not isolated from the chassis. Then it will just complete the circuit through the tool, which is all the Crocodile clip is doing.