Folding Tool seams are formed from two steel halves, permanently joined together. Handy sight holes assure proper depth alignment. 12F - 12" (31 cm) Folding Tool with 3/8" (9.5 mm) & 1" (25.4 mm) depths . 18F - 18" (46 cm) Folding Tool with 3/8" (9.5 mm) & 1" (25.4 mm) depths . Longer folding tool assures a more uniform fold. 24F - 24" (61 cm) Folding Tool with 3/8" (9.5 mm) & 1" (25.4 mm) depths. Extra long folding tool may also be used as a mini-brake by roofing and siding applications.