tabernacle
A hinged device allowing for the easy folding of a mast 90 degrees from perpendicular, as for transporting the boat on a trailer, or passing under a bridge.
tabernacle: the mast's fold-down hinge joint
A tabernacle is a pivoting base fitting that allows a mast to rotate 90 degrees and fold down along the boat's length. It consists of a sturdy metal block bolted to the deck or cabin roof, with a hinged pin that supports the mast heel (the mast's lower end) and lets it swing aft. This mechanism is essential on boats that must navigate shallow waters, pass under bridges with limited vertical clearance, or fit on standard road trailers for transport.
The fitting does real structural work. The tabernacle must handle the full compressive load of the mast under sail, sometimes tens of thousands of pounds on larger boats. It's typically fabricated from aluminum alloy, stainless steel, or cast bronze, and the pivot pin is a substantial bolt, usually half an inch in diameter or larger. The hinge must be precisely aligned so the mast doesn't bind when raised or lowered, and wear between pin and hole can develop slack over years of use.
Raising and lowering the mast requires deliberate technique. The standing rigging (upper shrouds and forestay) must be managed to prevent fouling, and the mast's weight demands mechanical advantage, either a hand-crank winch mounted to the tabernacle, or a tackle system rigged through the cabin. Getting caught between a lowering mast and the tabernacle block has caused serious injuries, so the operation is never rushed or casual.
Common problem points
Corrosion is the primary enemy, especially where freshwater collects in the folded mast position. Seized pivot pins, bent deck blocks from impact or improper lowering, and cracked welds at the deck attachment are routine repair issues in shipyards. The constant micro-motion during sailing also works the fitting loose; regular inspection of the mounting bolts prevents catastrophic failure.
The name itself derives from the movable wooden frameworks that housed the religious artifacts of ancient Israel, which were lowered and raised for transport. Early maritime engineers borrowed the term for a fitting that served a similar purpose: collapsible, portable, and field-repairable. It remains standard vocabulary in sailing communities, particularly among cruising boat owners and river navigators where bridge heights dictate the choice between a tabernacle mast and a fixed one.