Corbelling, where rows of corbels gradually build a wall out from the vertical, has long been used as a simple kind of vaulting, for example in many Neolithic chambered cairns where walls are gradually corbelled in until the opening can be spanned by a slab.
In medieval architecture the technique was used to support upper storeys or a parapet projecting forward from the wall plane, often to form machicolation where openings between corbels could be used to drop things onto attackers. This later became a decorative feature, without the openings. Corbelling supporting upper stories and particularly supporting projecting corner turrets subsequently became a characteristic of the Scottish baronial style.
Medieval timber-framed buildings often employ jettying, where upper stories are cantilevered out on projecting wooden beams in a similar manner to corbelling.
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