engages the standing seam over the top of the seam additionally a more aesthetically pleasing roof results when the aligned cinch straps 36 arranged in a head to tail relationship completely cover the standing seams formed by the adjacent roofing panels referring now to fig1 through 9 when assembling an endlap joint according to the present invention a first lower roofing panel 80 is positioned so that the upper end 87 of the roofing panel 80 is adjacent to the upper end of an already installed roofing panel while the remainder of the roofing panel 80 extends toward the gutter line a longitudinal edge of the first roofing panel 80 engages the longitudinal edge of the already installed roofing panel to form a standing seam a backup plate 20 is positioned adjacent to an already installed backup plate so that a shoulder 22 of the backupu plate 20 rests on top of a shoulder 22 of the already installed adjacent plate the backup plate 20 is positioned so that the upper end 87 of roofing panel 80 is inserted beneath the plurality of retaining tabs 26 a second upper roofing panel 90 is then positioned over roofing panel 80 and the backup.