If hooks are used to attach cages or buckets to the socket or thimble of a hoisting rope, the hooks shall be self-closing. (Sec. 101, Federal Mine Safety and Health Act of 1977, Pub. L. 91-173 as amended by Pub. L. 95-164, 91 Stat. 1291 (30 U.S.C. 811)) [48 FR 53242, Nov. 25, 1983]