In architecture, a machicolation is an opening between the supporting corbels of a battlement through which defenders can target attackers who have reached the base of the defensive wall. A smaller related structure that only protects key points of a fortification is referred to as a bretèche. Machicolation, hoarding, bretèches, and murder holes are all similar defensive features serving the same purpose: to enable defenders atop a defensive structure to target attackers below. The primary benefit of the design is to allow 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.