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