A small work, generally built of logs, to protect adjacent ports. Blockhouses were primarily constructed in our American colonies, because they could be immediately built from the heavy timber felled to clear away the spot, and open the lines of fire. The ends were simply crossed alternately and pinned. Two such structures, with a space of 6 feet for clay, formed, on an elevated position, a very formidable casemated work. The slanting overhanging roof furnished excellent cover in lieu of loop-holes for musketry.