This article is from the Backgammon FAQ, by Mark Damish damish@ll.mit.edu with numerous contributions by others.
The Jacoby rule is used in money games. It states, that a gammon or
backgammon may not be scored as such unless the cube has been passed
and accepted. The purpose is to speed up play by eliminating long
undoubled games.
The Jacoby rule is never used in match play.
 
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