1 2 3 4 E E E E * v c t * v X * - * handedness 1 2 3 R handedness 1 2 4 L handedness 2 3 4 L sheetS 1 3 4 sheetD 2 1 length 1 E 5 100 length 2 E 5 100 length 3 E 5 100 length 4 E 5 100