"To bid Mark is to lean far, far out over the abyss, suspended by a strand of dental floss."
- Grima Thanusual, 42 Theorist
As the quotation suggests, bidding mark is a risky business indeed - in bidding mark a player believes her team can secure every trick in a hand. Mark can be bid on any regular hand, although for obvious reasons, one would typically only consider doing this on an invincible or nearly invincible hand. In this case, it is not uncommon to bid 2-Mark in an attempt to derive additional gain from the fortune of a good shake.
To clarify the concept of a high bid, it must be understood that above the maximum point score of 42, "Mark", one is bidding on hands within a game. Bidding 2-Mark is generally the highest allowable starting bid, but subsequent players may outbid with a 3-Mark, then a 4-Mark and so on. The key here is that the winner of the hand gains marks toward the game victory of seven equal to the number bid, instead of the usual one per hand. This means that success or failure on high bids is far more critical than on normal bids. It is also sufficient encouragement not to make a high bid or, to an even greater extent, outbid a high bid without reasonable assurance of success. The flow of the game does not change on a Mark bid, but a much better hand is required for success than usual. However, there is another bid which puts even the breathtakingly risky 2-Mark to shame.
As the name suggests, gone is the dental floss security of the Mark bid - there is only the plunge and the abyss here. Bidding the big 3MP is something akin to throwing strategy to the wind, however there is still a level of tactics and maneuvering. In this bid a team has the opportunity to acquire a whopping three marks toward victory in one fell swoop, but they stack the odds against themselves in so doing. As the rules state, the player who makes this bid must have at minimum four of the seven doubles in his hand. However, it is the bidder's partner who both chooses the trump and leads. As such, 3-Mark has a set of nuances and tactics all its own.
From a purely theoretical standpoint, a player should never bid 3-Mark plunge. This bid will frequently transform an otherwise invincible 2-Mark victory into an unpredictable 3-mark swing. The bid is essentially ignored in competitive 42 for this reason. However, it is also one of the most exciting modes of play, and as such players who are found to have pulled four doubles but not bid 3MP should immedietly be branded spineless jellyfish and sentenced to walk the plank.
Winning at 3-Mark Plunge involves some luck, some mind reading, and some good forethought. The essential strategy is for the partner to call a trump that her team has most of, and after pulling out all the dominoes of this suit, hand off control to her partner so that he can play each of his four walking doubles in succession for the victory. If the partner has a viable trump anyway this typically works very well, because with the trump suit eliminated the partner only has six suits to throw to, of which her partner is certain to pick up on four - All the better if she has one or both of the other doubles. If, on the other hand, the partner has a weak trump option or no doubles, she must try and choose a trump of which the bidder has the highest among his four doubles.
For the stopping team, winning essentially consists of trying to maneuver into having the highest trump. Frequently, 3-Mark Plunge will end instantly when the partner calls a trump suit from which the opposition has the double. It is also worth noting that four doubles is the ideal number for plunging successfully - even bespined jellyfish do not call 3-Mark with five or six doubles because it severely reduces the chances of success.
Special Mark Rules
To make Mark bids more palatable, there are optional special rules a winning bidder can implement to improve the chances of victory. The most common among these is the follow-me rule, wherein play proceeds as usual with the notable exception that there is no trump suit. Strange hands with a scattering of high dominoes may succeed at this where having to pick a trump would guarantee loss. Most follow-me hands are a succession of dominoes that are walking after the previous domino in the series has been played. Frequently, they include some low dominoes which they attempt to trick opposing players into allowing to walk. For instance, a follow-me player might play a 6/6 followed by a 6/5 in hopes of eliminating fron play all the dominoes that could beat his lower 6/1. Another interesting Mark-only rule is calling 7's trump. These are all those dominoes whose dots sum to 7. Since there are only three of these, it's likely a single hand could contain all of them, making this a powerful option for a small set of specific hands.
The most outlandish of all Texas 42's rules is that of the Nel-O hand. Nel-O is the escape hatch of the shaker, and something most players will witness only rarely in play. In any hand in which the first three players pass on the bid, the shaker is forced to bid on her hand. Sometimes it is feasible to bid 30 and play as usual, but occasionally the shaker may have a hand that is so lowsy as to guarantee failure. In these cases, there is the option of Nel-O: Losing To Win. The shakers partner plays no part in Nel-O; He simply leaves his hand face down and does not participate. There is no trump, but the shaker has the option of calling doubles high, low or suit-of-their-own, and herein lies the first important decision. Since she is trying to lose, she wants the lowest hand possible, so obviously if the shaker has a lot of doubles, she should call them low, otherwise, she should call them high. An interesting point is that you can safely call doubles high with the 0/0 (and to a lesser extent, the 1/1) in your hand, because it cannot be lead to and so cannot win a trick. Suit-of-their-own is more useful in some situations where the shaker has doubles, but they are little use in covering for her other dominoes.
The shaker leads the first (and only the first, since the opponents must win all successive tricks) domino. Obviously, she should lead something likely or guaranteed to lose, but there is good motivation for putting a lot of thought in here - it is the only throw she controls. Best success is typically had when ditching a domino with one dangerous side and one low side on the first throw. For instance, it would be wise to throw the 6/1 here, since it will probably lose as a 6, but almost certainly win if an opponent throws the 1/0. After the opening, the opponents proceed as usual, with the previous trick's winner leading. The general theory of stopping a Nel-O is to throw a low domino which the shaker must beat, but one's partner can lose to. For the shaker, it is a matter of survival - using cover adequately and ditching threats at every opportunity. There are a lot of variables in Nel-O - there is an extra hand missing from play, with unknown dominoes, and subsequent tricks are stacked, making memory a factor.
The Texas 42 player who can successfully use basic tactics to build complex strategy, communicate effectively with his partner, and wage unrelenting psychological warfare on his adversaries will achieve victory...
... much, much more often than a complete dullard.
5/5 + 6/4 + 3/2 + 4/1 + 5/0 + 7 tricks = 42