This invention concerns an active reconfigurable stretch forming tool, and in another aspect the invention is a method of stretch forming. The tool comprises an array of extensible shape forming elements which are driven in extension to produce the same force per unit area across a workpiece during shape forming. An array of limit switches are located in front of the array of shape forming elements, such that each shape forming element is driven in extension towards a respective limit switch during shape forming. In use, each limit switch is activated by the workpiece as it is shaped and each switch, upon activation, prevents further extension of the respective driven element. The tool and method are useful in the forming of three dimensional shapes in solid sheet metal or mesh, to produce panels for reflector antennas.