There are many varities of blocks; some are better than others under certain situations. Which do you use?

Effective Blocking

Like a lot of unarmed fighting systems, Chongdo teaches its students about blocks. A block is an effective way to stop an attacker’s fist or foot; but it may not always be the best way.

There are a few types of blocks:

A deflection block.
Deflection. This is the most popular type of block: the opponent throws his fist toward your head, and you bring your hand, wrist, or forearm up to bounce his strike away. This type is very frequently used by fighters because it maximizes reaction time: literally, you do not stop his fist until it just about reaches your head. The problem with this block is that it only stops the strike, and nothing else.
A check block.
Check. This is an easy block that is seen in only a few fighting systems. The opponent begins to throw his fist forward into your head, but you drive your palm into his shoulder or biceps, forcing him to jerk to a stop. It also positions your hand for an immediate counter-strike already within his defensive range. The only downside is that you must identify his strike and move your own hand in faster to stop it. Because you are not extending as much as he is in the strike, this is not as difficult to sound as it first seems, and works very well for circular-style punches.
A grabbing block.
Grab. Many soft styles use grabs, in which you seize his hand or wrist in flight: either you will execute a throw, a flip, a pull, or execute a lock of some sort. Although this block presents the most possibilities (you’ve got his arm, so do whatever you want), repeated studies show that a person with moderate striking skills can hit you and return before you complete the grab. In effect, easier said than done. Students of soft systems who wish additional proof are recommended to practice grabs against bare-armed amateur boxers with some genuine sparring experience.
A trapping block.
Trap. The trap is a hybrid between a deflection and a grab. You strike the opponent’s incoming hand (just as with a deflection) but direct his hand across his body to promote an obstacle for his other hand. Your blocking hand is free to shoot in and strike him, or your other hand is ready to deliver a more powerful move. If you wish to grab, you can now do so as you have decelerated his strike sufficiently. Like a deflection, it buys you reaction time but sets you for an instant counterattack. Like a grab, it provides you a wealth of possibilities but does not require you to fumble for contact.

Deflection-type blocks work from a variety of ranges; the other three only work best at close ranges. This seems like a weakness, but is not: at longer ranges, students should duck or avoid swings rather than attempt an interception. At close ranges, this no-handed strategy is ill-advised; fortunately, blocking opens up the tactics allowed here.

Traps come in many forms. Some of the exotic sticking techniques of Wing Chun are nothing more than simple traps. The rhino-block of Muay Thai is a cleverly concealed trap: as the elbow comes up to protect the side of the head, it allows the same arm to hook, drive, snap, or crush a split-second later.

The important thing about checks, grabs, and traps is that, when done right, something is getting done. Deflections merely prolong contact: the next move is either you hitting back, or him trying to hit you again. With the other three, you can turn the block into a counterattack and end the fight.