Abstract: Modular panels having foam cores covered by metal skins are interlocked to one another by complementally formed bends in the metal skins. A flat is formed in one of the metal skins to introduce flexibility and play into the interlocking mechanism, and both interlocking skins have a transversely extending bend formed in them that makes a line of contact with the mating interlocking skin to reduce the friction between them and to allow lateral movement of the interlocked panels. The play and flexibility introduced by the flat enable adjacent panels to be interlocked to one another by a straight-in movement and by an angular movement known as a rock and lock.