www.lajollabridge.com By Maritha Pottenger
As Declarer, one of your jobs is to cut the lines of communication between your two opponents. This is often done by “holding up”—refusing to take a winner right away. In no trump, if you hold up once or twice, you may exhaust one opponent of a particular suit, so s/he cannot reach his/her partner in that suit.
The “Rule of 7” suggests that you subtract the number of cards you and dummy have in a suit from 7, and the answer tells you how many times to hold up if you have a single stopper in a suit. So, with 5 cards between you and dummy, you hold up twice. This ensures that if one opponent has 5 cards in the suit, your hold up will exhaust the other opponent of that suit; if the suit is 4-4, you are limited to only one more loser. With six cards between you and dummy, you hold up once. However holding up twice can also be right, limiting your losers in a 4-3 split to two if the four card defender cannot get in later.
Do NOT hold up if you cannot stand a switch to another suit. Just take your chances! Do NOT hold up if you could end up losing 5 tricks. For example, LHO leads a 4th best card and RHO plays the queen. You hold K109. Do NOT hold up! The AJxx(x) could easily be behind you. Take your King. If you hold KJ9 and RHO plays the queen, you can afford to hold up because your KJ is still one surestopper after RHO takes the queen.
Do not hold up if you can block the suit by taking the first trick. An example would be holding A10 opposite 9xxx and LHO leads a low card in the suit. If LHO has 5 cards, then RHO has a doubleton honor, e.g. QJ. By taking the first trick, you block the suit. The opponents will not be able to untangle their honors—without giving you an extra trick—before you have a chance to knock out one of their stoppers.
Do not hold up if you can block the suit by playing second-hand high. An example is: Q10x opposite Kxx with the suit bid on your right. LHO leads the top of a doubleton. Play the queen from dummy. If RHO takes Ace and plays suit again, let it run to the 10—ensuring two stoppers. If RHO ducks, you still have a second stopper. If RHO takes the Ace and shifts suits, you have gained time. Another example would be Axx opposite J9x in dummy. RHO bids suit and LHO leads the 10. Play the Jack from dummy and DUCK when RHO plays the queen (or king). If RHO plays the suit again, you are guaranteed two stoppers (let low card run to the 9; kill other high honor with your Ace and 9 is 2nd stopper). If positive LHO cannot get in again, OK to take 1st trick.
When you have two stoppers, but must knock out two high cards from the opponents’ hands, it is usually right to hold up once.
Holdings such as AJx opposite xxx or KQx opposite xxx count as 1-1/2 stoppers. Depending on who has the other high honors—and which opponent is most likely to get the lead next, you will duck or take the first trick. If king or queen (presumably from KQ109) is led on your left and you have AJx, ducking is best. LHO cannot continue without giving you two tricks. If a low card is led and King (or Queen) is played on your right (meaning other high honor is on your left), take the first trick IF LHO is likely to get the lead next [e.g., you have to finesse into LHO]. If RHO is likely to get the lead next, duck twice hoping to exhaust RHO of that suit. If a low card is led and RHO plays 10 or jack when you have KQx, you know that A10xx(x) or AJxx(x) is now behind you. If LHO is likely to get the lead next, take the first trick. If RHO is likely to get the lead next, duck (hoping to exhaust RHO of suit).
In suit contracts, hold-ups are most often avoidance plays. You are trying to avoid letting the dangerous opponent gain the lead. (The dangerous opponent is whoever can lead through your vulnerable honor holdings. So, with Kxx opposite xxx in dummy, RHO is dangerous opponent. With xxx opposite Kxx in dummy, LHO is dangerous opponent.) Often, you will have an opportunity to transfer a loser from one suit to a different suit in order to avoid the chance that the dangerous opponent will get the lead. For example, with 
AKxxxx 
Kxx 
xxx 
x opposite QJxx xx AKxxx xx with LHO leading Ace, then King of clubs, it is best to discard a low diamond on the 2nd club (rather than ruffing). Then pull trumps, set up diamond suit (probably with one ruff) and discard your losing hearts on the good diamonds. Without the diamond discard, RHO might get in with a diamond to finesse against your King of hearts.