This was decidedly risky, but it is not unusual to bid a four-card suit in such situations.

This reverse bid suggested extra values, but implied a four-card suit that he did not have.

A major-suit opening is limited and natural, but may be based on a four-card suit, perhaps with a longer minor.

West can be assumed to have a four-card suit, and South must have at least one top honor.

One answers the question, "When can you overcall with a four-card suit?"

South now assumed, naively against Zia, that there was a four-card suit on his left.

It was therefore forcing, with a four-card suit possible and no strength limitation.

Since his partner could have held a four-card suit, he chose three no-trump rather than four hearts.

Two no-trump was forcing, and asked South to show any four-card suit.

Experts are often ready to overcall in a four-card suit at the one-level, especially when not vulnerable.