(under subclass 309) Method or apparatus comprising (a) movement of one wall with respect to an adjacent wall farther than is need so that upon release of the moving force the wall will move by residual stress back to the desired position; or, (b) movement of one wall of a workpiece 180 deg. with respect to an adjacent wall where the final position of the wall is to be 90 deg. from either the first or the second position.
