Abstract: A box section frame member includes an upper channel-shaped member having the flanges partially telescoped into the flanges of a lower channel-shaped mender. A weld connection is made at the upper edge of the lower channel-shaped member. The flanges of the lower channel-shaped member are formed with integral struck out T-shaped tabs which project inwardly and are longitudinally spaced. The upper channel-shaped member is provided with correspondingly spaced T-shaped openings located to mate with the tabs in the assembled relation. The tabs and opening are made during the formation of the channel members which are pre-assembled by press fitting of channel-shaped members with the flanges and web portions thereof deflecting to permit the movement of the openings past and into locking engagement with the tabs.