General Order 64-A
Detailed Construction Requirements For Trolley Lines
(Class T Circuits)
Messenger and span wire attachments shall have a strength at least equal to that of the strand to which they are attached.
Cedar and other soft-wood poles to which any span wire or messenger having an ultimate strength of 5000 pounds or more is attached, shall be protected by suitable shims, and where necessary with hooks, lag bolts or other equivalent means to prevent the span wire or messengers from slipping along the pole.