(1) Safety straps of appropriate size must be placed on all high lead blocks; and other blocks whenever practicable. Safety straps must be shackled (with the closed end of the shackle up) to a guyline that extends as near as possible at right angles with the power unit, but must not be on a guyline with an extension within one hundred feet of the tree. When the top guyline on which the safety strap of the high lead block is fastened is changed, the safety strap must be attached to another guyline or the loosened guyline must be tightened after the change.

(2) All tree straps must be at least 1/4-inch larger than the pulling line. If impossible to use a safety strap, all tree straps must be 1/2-inch larger than the pulling line.

(3) Lead blocks used for yarding, swinging, loading, and unloading used in wood spars must be:

(a) Designed and constructed for this purpose;

(b) Bolted with at least two bolts through the shells below the sheaves in a manner that will retain the sheave and line in case of bearing pin failure (this does not apply to haulback lead blocks); and

(c) Mainline blocks have a sheave diameter of at least twenty times the diameter of the mainline.