Alloy Goldilock spring-loaded lock and toggle, the ideal solution for those classes which don't use mainsail halyard but require a quick-release mechanism.
The fitting is riveted inside the top of the mast with a toggle fitted to the headboard to fit over the plunger. The plunger is released when the release wire (led to the base of mast) is pulled on.
Stainless Steel compression spring, plunger and channel support from are anodised alloy.