Two Bastions were placed at opposite corners with most of their walls outside those of the Fort.  The floor of the second story was strong enough to support movement of the brass barreled cannon.  Rifle slits made it possible to use three riflemen from any side. One blockhouse doubled as a powder magazine and armory.  Each blockhouse had a small observation platform on top as well as a flagpole.  Although Fort Benton was never under siege, its large blockhouses and 14" thick walls would have discourage any thoughts of attack upon the traders inside.