Abstract: For holding together flexible materials, such as roll-up display screens, edge-to-edge, very thin and narrow flexible magnetic strip (3) is co-moulded edge-to-edge with non-magnetic flexible strip (4), one face (7 or 5) of the combined strip (1 or 2) being suitable for the application of an adhesive, e.g. in the form of double-adhesive tape (8, 9), and the other face (5 or 7) being provided with indicator means for the polarity of the magnetic portions (3) e.g. different colouring pigments in the non-magnetic portions (4) of co-acting combined strips, or impressions such as a single continuous groove (6) for N-polarity and a pair of grooves (10) for S-polarity.