Halyard locks were mostly designed to manage big loads on big boats. They solve most of the problems that you will encounter on a halyard such as stretch, chafe and mast compression. The system is quite simple: it locks the sail into the mast once it is hoisted without relying on a clutch or a winch.
There are different systems on the market for which you normally need a “trip line” – a dedicated line that goes up the mast to disengage the lock and be able to drop the sail.
Solo sailors quickly saw some of the weaknesses to the early systems…they challenged the engineers at Profurl & Facnor design offices on how to improve the systems and get rid of the “trip line”.
The system that was subsequently developed and is available now only needs the halyard itself to be locked and unlocked. Basically, the sail locks itself once you arrive at full hoist. In order to unlock, you simply pull the halyard down and the system unlocks itself.