29 C.F.R. Appendix D to Subpart R of Part 1926
(1) When used to control access to areas where leading edge and initial securement of metal deck and other operations connected with leading edge work are taking place, the controlled decking zone (CDZ) is defined by a control line or by any other means that restricts access.
(2) Control lines consist of ropes, wires, tapes, or equivalent materials, and supporting stanchions as follows: