Bidding Over One Club - BOOC
Probably the single most used card in the bidding box is the 1 call. (And for sure the least used is the 7NT card.) Below is the treatment we use when the opponents open one club...
The Major Suits
Part of our BOOC bids are similar to the Michaels convention, which always promise at least 5-5 in the two suits. Our agreement is to use Michaels with 5-5 also, but with a guarantee of perhaps 13+ points. BOOC is used with lesser hands, often with 4-4 or 4-5 in the majors and only 7-12 points, certainly not enough strength to push the bidding to the second level.
Overcall with One Diamond to Show Both Majors
This is an artificial bid and must be alerted... The description is that it shows both majors, but not necessarily 5-5 in the two suits.
Either of these hands would qualify:
Hmmm... okay, but what if you actually have a diamond suit, or maybe a diamond suit with one of the majors?
Double with Diamonds
Although the double is a transfer to diamonds, showing at least a 5-card suit, the doubler may also have a 4-card or 5-card major. Here is a typical hand:
We do not use the traditional 1NT overcall. Instead, we show two suits: The top and bottom unbid suits.
Two Lower Unbid Suits
A jump to 2's shows the diamond suit, but it also promises a heart suit. The two lower unbid suits.
BOOC allows us to show any single-suited hand, and all two-suited hands. We give up the ability to show a balanced hand with 15-17 points.
Although most of the time the double will be a diamond suit, we also use it to show a strong notrump hand.