A very important part of Taekwon Do are blocking techniques. Indeed they are somewhat more important than attacking techniques, as you could not attack, if the opponent has knocked you down before. The name block does not reflect it correctly, as most of the techniques will not block an attack, but deviate it. A hard block, force against force could do more harm to yourself than to the opponent. It could be only a very last resort. So most of the blocking technique really deviate the attack.
One more point is that any blocking technique could be used as an attack too. Also most of the attacking techniques could be used for blocking. This is an concept that is hard to understand for beginners. Even advanced students may have problems with it, but for an example, you could use exactly the same movement as Hadan Makki for an attack to the genitals. You could also say this technique is a hammer fist, but this example should only show that a very advanced student could expand his/her possibilities if he/she comes to an more flexible view of the techniques, instead of pressing them in a fixed scheme.