blockhouse, small fortification, usually temporary, serving as a post for a small garrison. Blockhouses seem to have come into use in the 15th cent. to prevent access to a strategically important objective such as a bridge, a ford, or a pass. Later the term was broadened to include all detached and isolated small forts, especially those in country just captured from an enemy. The typical blockhouse was of two stories, with an overhanging second story and loopholes on all sides for gunfire. In the North American colonies, blockhouses were used in frontier communities as protection against Native American attacks; they were built of timber or stone (in New England) or of logs banked with earth (in the South and West). The frontier blockhouses were frequently surrounded by palisades and thus were technically stockaded forts. The principal use of blockhouses in present-day military fortification is in defending isolated units against small-arms fire.