Jamcleat

Sailors know what a jamcleat is, but there did not seem to be a definition on the web, only pictures.

Some particularly pretty ones can be bought at Wooden Boat Fittings.

A jamcleat is fixture to which running rigging is made temporarily fast. For landlubbers, that would be a thing to which you fasten a rope that needs to be adjusted. A jam cleat is a cleat that will hold line against the load without a knot. Generally it is a narrow pinch point in a conventional deck cleat or sometimes a mechanical cam which wedges the line and holds it while you take care of other things. When you return, a flick of the rope releases the grip and lets the line be adjusted to a new setting. They’re a blessing as they give you a rest from holding a sheet (the rope that controls the set of the sail). It can be a problem when it will not let go, gets tangled or fouled and will not let the rope run free when it needs to.

‘Tis advertised in Boston town, New York, and Buffalo,
500 brave Americans, a whalin’ for go to go
Blow ye winds in the morning
Blow ye winds hi-ho
Haul away your running gear
And blow, boys, blow.

Traditional

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And such is the Jam Cleat.