William Howe of Massachusetts patented the Howe truss design in 1840. It is really an elaboration on the multiple kingpost design where by two heavy metal rods are substituted for the vertical timbers. There are also variations on this pattern that add a second diagonal timber to the original single diagonal of the multiple kingpost and/or another diagonal timber running in the opposite direction between the vertical rods. Some accounts indicate that the Howe design provided a bridge that was stronger than the all-wood structure; as a result, it became the forerunner of iron bridges.