Bracket nut. Left.CREW CAB. PRODUCTION-TYPE 3. Right.CREW CAB. A solid metal or plastic block with a threaded hole in the center which is used to tighten or adjust the ABS Hydraulic Control Unit. A solid metal or plastic block with a threaded hole in the center which is used to tighten or adjust the Running Board Step Pad. Running Board Nut. Hex. Flanged. ABS Hydraulic Assembly. Adjust motor. Center. Mount. Running Board Step Pad.