in structure both the front and back frame members 16 18 include an inner facing side 32 and an outer facing side 34 the inner facing side 32 is provided with rib members 36 and 38 at the opposite ends the rib members 38 are sized and configured for snug fitted receipt within the recessed channel 24 wherein the front or back frame member 16 18 is fitted to the longitudinal frame members further the ribs 36 fit snugly against the inner surface 20 and the footing 29 the ribs 36 and 38 serve to reinforce the frame assembly 12 providing structural rigidity in order to facilitate attachment of the front and back frame members 16 18 to the respective longitudinal frame members 14 14 39 without the use of tools a double sided adhesive material 40 is provided on the inner facing side 32 of the front and back frame members at the areas where the inner facing sides 32 engage the ends 23 25 of the longitudinal frame members in manufacture the exposed surface of the double sided adhesive may be provided with a peel away film which is removed at the time of assembly by fitting the front and back frame members 16 18 in position against the ends 23 25 of the longitudinal frame members so that the.