Cover
Make the fewest groups in which every pair meets at least once; stop when the last pair has met.
Dinner seating changed each course so that nobody misses anybody.
Seen in Tom Johnson, Kirkman's Ladies
Try it on your work
Take six materials. Make the fewest small boards of three that you can, so that every two materials sit together on at least one board. Stop when the last pair is placed.
Take six words from your project. Write the fewest sentences of three of them that you can, so that every two words appear together in at least one sentence. Stop when the last pair is used.
Nine people meet in threes over short rounds, arranged so that every two people talk in the same three at least once. Stop when the last pair has met.
How it has been used
Choose a few groupings so that everything meets everything else at least once: seating rounds for a long dinner, sample boards on which each material sits next to each other material somewhere, a set of photographs in which every two people appear together once. The move forces economy: as few groups as will do, and no pair left out.
Where it leads
Grouped under Spread it across more people or parts