This is one of the most ABUSED conventions in all of bridge.

Originally its use was as follows:

Dble is a 1-suited hand, PENALTY oriented. It showed a good suit with

entries. (e.g. something like Ax xxx KQJTxx Kx).

2C shows clubs-hearts

2D shows diamonds-hearts

2H shows majors

2S shows spades and minor.

Nowadays it has been perverted so that most people use the double to mean

ANY one--suited hand; even a broken suit.

Advancer bids 2C to find out. Some require a good suit to double, so that advancer can leave the double in with a fair balanced hand. 2m = m and H, at least 5-4 in the two suits 2H = majors 2S = spades and a mystery minor (bid 2N to find out which) 2N = minors Some use 3-level bids as natural, showing a longer suit than the double, while some use it to show a 3-suiter short in the bid suit