Abstract: A fastening device (1) for fastening polyurethane screening panels (6,7) to a screen (8) is made up of a composite fastener and a disc stringer support. The composite fastener is a steel bolt (2) and nut (3) with a polyurethan holding component (4) and a polyurethane cover (9) for the bolt head. The disc and stringer support is a stringer (31) serving as a joist spanning between girders of the screen frame, the stringer (31) having no flange and being narrow and deep, with discs (35) set in the top surface of the stringer at spaced apart positions, having a hole (36) in each disc for the bolt and nut and a recess (38) in the stringer underneath each disc for the nut. The bolt and nut have a toggle (14) which allows insertion into the hole in the disc and tightening the bolt and nut entirely from above the screen.