Fourth Suit Forcing Auctions

Fourth suit forcing to game is something most players play nowadays but I think many people don't know some of the implications of bidding fourth suit. Why do we bid fourth suit forcing? Because we want to be in game but don't know what strain we should be in or because we want to make a forcing raise but bidding 2, 3, or 4 of the suit would all be passable, and/or because we want to make a slam try.

Take this auction for example: 1C-1H-1S-2D-2NT-3S. Opener has a balanced minumum with 4 spades and a diamond stopper. Many people do not know what responder is showing here. He is making a slam try in spades. He could not bid 2S (nonforcing), 3S (inv), or 4S (sign off) so the only way to raise spades and have it be forcing is to bid 4th suit and then bid 3S. A good hand for this would be: AJxx, AKxx, Kxx, Ax. Take out a king and it's a simple 4S bid over 1S. Likewise, responder has to bid fourth suit to make a forcing club or heart raise.

As with new minor forcing, many people think of 4th suit as just showing a good hand with a 5 card major, which it frequently is, but people need to keep in mind that it could be a hand with too much to just jump to game, and/or a forcing hand that does not have the 4th suit stopped.