Texas Hold’em is normally played with the two players to the left of the button putting up blinds. Typically the small blind is one half or two thirds the amount of the big blind with the big blind being the amount of a “small” bet (in a 20-40 game the blinds are 10 and 20). There is a seldom used optional third blind called a straddle. The player to the left of the big blind may put up an amount that is double the big blind which allows him to act last before the flop (in a 20-40 game the straddle is 40).
In a full handed limit hold’em game there is no reason to ever straddle. You would be putting up an extra blind out of position. Some players feel it enhances their image when entering the game to post a live straddle (you can straddle and come in one hand earlier than waiting for the blind). Despite small perceptual advantages, in full games straddling has little real utility. In shorthanded games, however, the straddle can become a powerful weapon.
As a game gets short the hands you will open for a raise increase dramatically. Often against opponents that fold too much you will find you want to raise any hand. When you reach this point you should look at a straddle. By straddling you are able to increase the stakes and give yourself last option before the flop. The most extreme case is a three handed game where you would want to always straddle on the button (this is such a strong move that some poker rooms have a rule that outlaws straddling in a three handed game).
In a three handed game the button has a unique opportunity to go last in EVERY betting round by straddling. The straddle has a by product of producing a larger pot before the flop. In shorthanded poker pots are often won by betting and bluffing. Producing this large pot increases the reward for stealing the pot and since you were planning to steal anyway, you might as well get the most for your money (if you are playing three handed and waiting for a good hand you should take up something less competitive like knitting).
In a four handed game the straddle is not automatic. You should still consider straddling if the big blind or the button folds too often and will lay their hand down to your straddle. When the game becomes five handed it is generally too full for a straddle to worth the investment.
When you straddle you are making a significant investment in the pot. Typically if you are raised you should always call (in a 20-40 game you have put 40 in the pot and it is another 20 back to you); you will be going last on the flop and you are getting at least 5 ½ to 1 on the call. A pot that has been straddled and raised has at least six and a half bets in it, so on the flop if you are waiting to flop a pair or a good draw you are playing too tight.
A straddle often strikes fear in the “ABC rocks” that are typical of daytime games in Las Vegas and other venues. Most players are inexperienced in short handed play and they are accustomed to a straddle being the mark of a weak gambling player. As you venture into short handed games if you add the straddle to your arsenal you will find you are stacking chips while everyone whispers about how bad you play.