Trial Bids

When you have a fit (8 cards) in a major suit and opener has a strong hand but a three card weak suit, trial bidding is a way of finding out to what degree the responder can cover the weak suit.

If opener bids 1S or 1H and responder bids 2 of the same suit, then a fit is agreed.

The opener with a strong hand bids any suit with 3 losers (a trial bid) to ask whether partner can cover tricks in that suit.

If responder has 1 loser she bids 4 of the agreed suit. 

If 2 or more losers and maximum points 8+, she bids 4 of the agreed suit.

If 2 or more losers and fewer than 8 points, she bids 3 of the agreed suit.

If you are using trial bids then once a suit is agreed the rebid in a new suit is always showing a weak suit.

i.e.  1S  pass  2S  pass  3C (weak suit)  pass - 4S (if one loser in clubs) 3S ( if two or more losers in clubs).