The weak jump shift is probably the most misused treatment/convention in duplicate bridge. The requirements for a weak jumps shift are:
A hand too weak to bid at the one level
No aces and no kings outside the bid suit
A singleton or void in opener's major suit or no more than three cards in partner's minor suit
Hand 1:
QJxxxx
x
xxx
xxx
Bid 2
in response to partner's one of a suit opening bid
Hand 2: AJxxxx
xx
Kxx
xx
Bid 1 in response to partner's one of a suit opening bid. With seven points and an ace you should bid
1. (If your partner opened 1 your doublton heart would be another reason to not bid
2.)
Hand 3: Qxxxxx
xxx
Kxx
x If partner opens
1 bid 2. If he/she opens 1 bid 1 - with five high card points and a singleton in a suit not bid by partner you are to strong to make a weak jump shift.
If your partner opens 1 you should bid 2 - never make a weak jump shift with two or more cards in partner's major.
Hand 4:
5
AQ1098
KJ6
AK65 If your partner responds 2 to your
1 opening bid you must pass.
Partner probably has 2 or 3 spade losers, a diamond loser or two and possibly a club loser. Also your hearts would be of little value to partner who should have a singleton or void in hearts. A double of a
3 or a
3 reopening bid would probably be a good bet.