Although the score may sometimes warrant a redouble without
extraordinary strength, a redouble practically avows the ability
to take six, and probably, seven tricks. In estimating your hand
consider the possibility of finding all the remaining trumps in one
hand, and do not value honours in the side suits too highly, for if
he holds great trump strength the maker is probably short in the
other suits. A redouble at “no-trump” indicates protection in every
suit.
The dealer should often redouble, not so much on the strength of his
hand, but to the score; knowing that should the adversaries win the
odd trick the game is lost, and that his redouble will equalise the
situation and make it possible for the odd trick to win the game for
either side.