The arm section is spring powered and automatically folds back in when no force is exerted on it The product does not protrude when the arm is folded in, creating a neat design and ensuring safetyCan also be mounted to sheet metal using the NF A round type is also availableWARNING: This product can expose you to cadmium, hexavalent chromium, lead, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information, go to www.P65WARNINGs.ca.gov.