Rope lock

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A rope lock is a device used in a counterweight fly system to keep a rope from moving. It consists of two steel claws which are pushed against each other to keep friction against the rope. A long steel handle (usually covered in a red rubber grip) engages the lock when vertical, and releases it when horizontal. A safety, a steel ring through which the rope is threaded can insure that the rope lock cannot be accidentally released.

Rope locks are designed to only hold in-balance loads. They are not designed to keep an out-of-balance line set in place. Most rope locks are only rated to hold a 40 pound (20 kg) difference. Misuse of the rope lock is a very common source of rigging accidents, especially among students. For this reason, proper loading technique is very important for safety in theaters.

Some more expensive rope locks exist which will not allow an operator to unlock it if it is too out-of-balance. These reduce the number of accidents, but also cause inconvenient loading situations. Expense also prevents many theaters from adopting them. Most rope locks have a hole through them to allow the set to be padlocked closed, to prevent accidental use of the set. This may be used, for example if a set piece is flown underneath the batten, and flying the batten would cause a collision.

Rope locks are attached to a locking rail which provides structural support and holds them at a level easily accessible for rail operators. When being installed, ropes must be threaded through the rope lock and the safety before it is tied off to the arbor.