Fort Nez Percés was built with a double palisade, unique among North West Company forts. The inner wall was 12 feet high, and a five-foot wide "strong gallery" was located between the two walls. The storehouse and dwellings were within. Trade was conducted via a small hole in the inner wall. The outer palisade was made of planks 20 feet high and 6 inches thick, and topped with a range of balustrades four feet high. Towers were located at each of the fort's four corners; these contained large water tanks for fighting enemy fire. Soon after the post was built, Alexander Ross said it was "the strongest and most complete fort west of the Rocky Mountains, and might be called the Gibraltar of the Columbia."