This is a good dance when there is a significant gender inbalance. It is best done with one man with two ladies or one lady with two men, but not a mixture of both. Each memeber of the trio becomes part of one of 3 concentric circleds. The inside and outside circles being made up of people of the same gender and the middle circle being made up of people of the other gender. An y people of the same gender as the middle circle who do not have partners should stand in the middle of the set.
As in any ninepins type dance, the music should stop at random somewhere in the B2 or even in the next A1.
Haystack Folk Club was the ceilidh (folk song and dance) club at London University which ran from Sep 1969 for about 5 years, and where I started calling regulalry. The dance is a mishmash of various other dances, eg Rebecca's Roundabout, Lights Out, Devil's Ropundabout etc.
For a long time I used to carry a bar of soap with me as a p[resent for the eprson who was left in the middle the most times!