The invention disclosed relates to fabricated rigid sheets profiled for engagement with adjacent similar sheets for assembly as a panel having sufficient rigidity to enable sufficiently large areas to be produced for the construction of van bodies, domestic and other building, caravans and road signs. Each sheet is of substantially rectangular shape with rearwardly extending flanges at each of the opposed longitudinal edges arranged supportingly to engage a corresponding flange of an adjacent similar sheet in assembly. One of the flanges is formed with at least one and preferably a plurality of spaced openings and securing means is associated with the other of the flanges for engagement in the openings of an adjacent similar sheet. Preferably the flanges connect to their respective longitudinal edges by folds one of which is formed with spaced apertures and the other of which is dimensioned to be received in the one fold of an adjacent similar sheet and has projections associated therewith for engagement in the apertures of the adjacent similar sheet. The projections may be stuck out of the rear wall of the inner fold or may be formed on a securing strip dimensioned to be received in the inner fold in which case the projections extend through apertures in the rear wall of the inner fold.