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