General Motors realized that after larger work trucks left the factory some owners would want to lengthen or shorten the side frame rails. Replacement beds would sometime require a different wheel base.
Therefore, as a warning GM painted or etched letters to tell owners the importance of a good, safe connection after the frame is cut. The attached photo shows a 1936 Chevrolet still showing this lettering on the inner frame rail. It is understood a similar warning is also on more modern trucks. Note: Even in the mid-1930’s the attorneys of General Motors were suggesting these warnings be visible to lessen laws suits!
1936 1 ½ ton from a farm in Western Kansas. Still displays the warning after 80 years! Seen just after the cut. Sorry photo does not help seeing the letters!