Handedness. This is the only board in the family that will group four players by the hand they threw with or the side they hit from — a fact every baseball fan half-knows and almost nobody recalls on demand. It is usually the group that survives longest.
Two ways that look alike and are not: the teams a player appeared for at any point, and the club he debuted with. Careers in this sport are long and well travelled, so a name can honestly belong to several franchises while belonging to exactly one debut.
Round career totals that the record book itself treats as thresholds — a count of stolen bases, of home runs, of strikeouts. Every member has cleared the same bar, so the group is checkable to the season rather than argued about.
The voted ones, by their proper names, including the rookie award and the season honours. Because these have been awarded every year for a very long time, an award group ranges across eras more widely than almost any other kind on this board.
Occasionally, and they are the ones people remember: four surnames that are also car makers, or occupations, or animals. The names have nothing else in common — not a team, not a decade — which is exactly why the group hides until the other three are gone.
