This is a tagger, and is the basis for the C1 call Chase Your Neighbor.
\syhlines{b4n,g4n,b1n,g1n}
\syhlines{g4n,g1s,b1n,b2s}
before Chase Chain Thru and Scatter Reaction
after
From back-to-back couples, the belles U-Turn Back to the right,
and all Box Circulate. You are now at the 1/2 tag position.
Proceed (or back up) as required.