Closing edge faces of multi-layer panels

A multi-layer panel structure (1) comprising three spaced sheets (2,3,4) of polycarbonate material is closed along an edge face by means of a closure (9) comprising an air-permeable filter strip (10) and a weatherproof closure strip (11). The filter strip (10) covers the edge face of the structure and prevents the ingress of dust and other solid matter into cavities (5,6) between the spaced sheets. It is enclosed by the closure strip (11), which is formed as a plastics extrusion and comprises upper and lower arm portions (12,13) which are joined by a base portion (14) and grip an edge portion of the structure. A ventilation duct (17) is formed between the filter strip and the base portion of the closure strip. The filter strip may be bonded to the closure strip, by means of an adhesive, prior to application of the closure (9) to the panel edge.