Abstract: A concrete mould employs resilient side shuttering, made of rubber for example, which is prevented from deflecting, when concrete is poured, by tensioning wires extending along the length of the shuttering. Pieces of the shuttering, forming the sides of a casting box, extend between fixed end plates having a series of holes to receive the tensioning wires for adjusting the modular width of panels cast in the box. A series of apertures is provided in each piece of side shuttering so that pneumatic core formers can be inserted through aligned apertures so as to extend across the casting box. Different types of joint formers, either fully or partly resilient, can be located about the core formers, each joint former having a series of grooves to receive reinforcement or tensioning wires or rods. When inflated the pneumatic core former locks the joint formers in place. Opening formers can be made from the shuttering and the joint formers.