First a generous-size serving tray, then a bed table with short legs that fold down from the underside this versatile unit finally becomes a TV snack table by a quick change of legs. The short legs are fitted in a frame that is held inside the tray by the ingenious use of Tee Nuts and thumbscrews. The projecting screws slip into short lengths of tubing “force-fitted” in holes in the ends of the leg frame. When the long legs are to be used, the thumb-screws are backed out, the frame removed and the legs installed. The screws fit in holes in the upper ends of the legs, and are held by nuts turned against flat washers.
Source: Workbench Magazine May-June 1967