Chock-a-block

Describes two blocks hauled together so that no further purchase movement remains.

In a tackle, the moving and fixed blocks become chock-a-block when their shells or fittings meet. Continuing to haul cannot shorten the tackle and may overload the line, fittings or structure.

The expression now also means completely full, crowded or tightly packed. Its nautical sense should not be confused with a chock, the fitting used to guide a mooring line.