Ford tells SAE International's Automotive Engineering International magazine that F3T (Ford Freeform Fabrication Technology) involves two slightly-offset styluses applying pressure to opposite sides of a sheet metal blank as they move along a prescribed path in unison across it. CNC technology and robots are used to guide and control the styluses against the sheet metal, which is clamped around its edges inside an enclosure. Read the AEI article at http://www.sae.org/mags/aei/12385.