Abstract: A metal form has a flexible panel member with a perimetral flange projected laterally from one side thereof. Each of a pair of transversely opposite side sections of the flange is segmented by a plurality of longitudinally spaced V-shaped notches having their apices adjacent the one side of the panel member to provide for a lateral flexing movement of the panel member to a preselected shape. With the panel member in the predetermined shape, the segments in each of the flange side sections are connected together against relative movement to retain the predetermined shape of the panel member. In a first preferred embodiment, each flange segment is connected to an adjacent flange segment by a flexible metal strap. In a second preferred embodiment, extended flexible metal straps are used to interconnect a central flange segment to each of the pair of adjacent flange segments.