Machicolation

Machicolation
Cutaway of a medieval wall. The machicolation is labelled G.

In architecture, a machicolation (French: mâchicoulis) is an opening between the supporting corbels of a battlement through which defenders could target attackers who had reached the base of the defensive wall. A smaller related structure that only protects key points of a fortification are referred to as Bretèche. Machicolation, hoarding, bretèche, and murder holes are all similar defensive features serving the same purpose, that is to enable defenders atop a defensive structure to target attackers below. The primary benefit of the design allowed defenders to remain behind cover rather than being exposed when leaning over the parapet. They were common in defensive fortifications until the widespread adoption of gunpowder weapons made them obsolete.