1. To consume the opponents’ bidding space, and so clutter their auction.
2. To indicate an opening lead - and subsequent defence - to partner.
3. To make a contract.
4. To pave the way for a profitable sacrifice (i.e. declaring a failing contract, but losing fewer points than would have been lost by letting the opponents declare).

Because holding a powerful hand for the overcall is only relevant in one case above (3), it is of secondary importance to holding a powerful suit. Whereas an opening bid can be a weak four- card suit, an overcaller must have a decent five- card suit. My recommendation - and I practice what I preach - is NEVER OVERCALL ON A FOUR-CARD SUIT.

The corollary to an overcaller guaranteeing (at least) a five-card suit is that the responder only needs three cards to support. Witness this North - happy to support his partner’s overcall at the Four-level with just three cards.

Take South's cards and play this deal