General Order 128
 Section IV
 Requirements for Communication Systems
 
42.7    Covers
       
Manholes and handholes, while not being worked in shall be securely
  closed by covers of sufficient strength to sustain such loads as may reasonably
  be imposed upon them, and arrangement shall be such that a tool or appliance
  shall be required for their opening and cover removal (Also See Rule 17.8
  and Appendix B, Fig. 9
).