An apparatus assists in retaining a rope in connection with a sheave on a boom. The apparatus includes a retainer supported by the boom for swinging outwardly relative to the sheave from a first position adjacent to the sheave for assisting in retaining the rope therein and a second position for facilitating removing the rope from the sheave. A holder may be provided for holding the retainer in the second position, so that the operator's hands are freed for other tasks. A receiver may also be provided for temporarily receiving a locking pin once removed from the retainer, thus helping to guard against loss.