Centers Thru and Close the Gate, or Put Centers Thru and Close the Gate

Put Centers In, then Twist the Line.

\sxvlines{g4n,g1n,b3s,b4s} \sxvlines{b1s,b2s,g2n,g3n}
4 2 1 3 3 1 4 2 1 3 2 4 2 4 3 1
before Centers Thru and Close the Gate after