Abstract: A conveyer carries in series sheets of card or the like, having rectangular central apertures. When a layer of adhesive has been applied, a portion of flexible strip, which is wider than the central aperture, is applied to the central part of the lower face of each sheet. There is deposited on the lower face of this strip portion a layer of adhesive which is narrower than the central aperture, and a strip of card or the like is then applied to this layer. The inlet and outlet margins of each sheet are then sheared along parallel cutting lines which intersect the central aperture at right angles. When the corners have been trimmed, the margins of the sheets can then be turned over and stuck to the lower face.