The arm section is spring powered and automatically folds back in when no force is exerted on itThe 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 50D or NF 50 bracket (sold separately)A square 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.