view of a third embodiment of a cross member indicated generally at 40 that is adapted for use in a joint with the side rail 13 illustrated in fig1 2 and 4 in accordance with this invention as above the cross member 40 is formed from first and second c shaped structural members 40 a and 40 b that are oriented to face inwardly toward one another and are secured together to form the closed channel structural member the first c shaped structural member 40 a has a pair of apertures 40 a u2032 formed through the web thereof similarly the second c shaped structural member 40 b has a pair of apertures not shown formed through the web thereof preferably the apertures 40 a u2032 formed through the first c shaped structural member 40 a are respectively aligned with the apertures formed through the second c shaped structural member 40 b the upper surface of the first c shaped structural member 40 a has one or more raised dimples 41 or similar embossments formed thereon each of the dimples 41 is relatively small and circular in shape and extends a predetermined distance above the upper surface of the first c shaped structural member 40 a the above described reinforcement member.