Weak two-bids are an extension of preempts (one level lower and one card fewer than opening at the three level), but all preempts contain roughly the same number of point (6 - 9 high card points.) The only difference when considering the level opened is how many cards there are in the suit.
♠ AKJ1083 ♥74 ♦42 ♣965 (six cards in spades) open 2♠ (Weak two-bid)
♠ AKJ10832 ♥7 ♦42 ♣965 (seven cards in spades) open 3♠ (Preempt)
♠ AKJ109832 ♥7 ♦4 ♣965 (eight cards in spades) open 4♠ (Preempt)
Weak two-bids can be made in diamonds, hearts, or spades, but not in clubs. 2♣ is reserved for the powerful game force hands. Weak two-bids have good 6-card suits and 6-9 points, e.g. ♠ AKJ1083 ♥74 ♦42 ♣965. This hand has eight high card points, and two length points for the fifth and sixth spade, (= 10 total points), making it perfect to open a weak two-bid, 2♠. It's not strong enough to open 1♠.
So, don't open a weak two-bid on 10 or 11 high card points (except in 4th seat), because this will be too strong, and it would have been better to open 1♠
(e.g. ♠ AKJ1083 ♥74 ♦K2 ♣965). The reason this matters is that partner will misinterpret your hand, and think you have a weaker hand. They will respond based on a wrong image they have of your hand.
A good suit is needed too. This depends a bit on vulnerability and where you're sitting at the table. Most of the strength should be concentrated in the six-card suit, typically with two of the top three honours, or three of the top five. Like preempts at the three level or higher, the weak two-bid is both obstructive and gives a good description of the hand.
The most favourable vulnerability is your side not vul and theirs vul. The least favourable is the opposite; your side vulnerable and theirs not. The other two vulnerabilities (nil vul and both vul) are about the same in the degree of danger of opening with a weak hand.
If your side is vulnerable you should probably have a suit headed by three of the top five honours, e.g. ♠AKJxxx or ♠AQ10xxx or ♠KJ10xxx.
If your side is not vul, the suit quality could be less eg ♠KJ9xxx or ♠QJ9xxx or ♠A109xxx
In first or second position, you need six cards in your suit to open a weak two-bid, but if the bidding goes p p to you in third seat, relax the rules a bit, not vulnerable, because the hand on your left will be marked with a lot of points. So open with a good five card suit, and not much else. Let's say you hold this:
♠ AQJ109 ♥74 ♦10962 ♣96 and the bidding goes p p to you. Open 2♠ because partner is already a passed hand, the contract is unlikely to be your side's, and your bid is lead-directing.
In the balancing seat, when the bidding has gone p p p to you, a weak two opening is around 12 points with a good six-card suit. The reason is you're not trying to preempt the other side out of a contract, because they had a chance to bid, and they chose not to! e.g. ♠ AK10983 ♥74 ♦K2 ♣965 You're giving partner a perfect description of your hand.
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