Last thursday we were running the yellow belts through an application for the lower block and upper block combination in Dan-gun. I've posted on this before (Dan-gun: Defence against a kick punch combination).
The technique requires you to use the folding action for the lower block to deflect a mid level kicking technique. The lower block strikes the leg. The folding action for an upper block blocks a punch and the upper block strikes the attacking limb or neck.
Putting them through their paces, I then demonstrate what it is like doing it at full speed. Then I show it, repeeating the moves a few times without stopping. This folding and blocking then folding and blocking creates a 'windshield wiping' effect - it's a very natural circular movement that can be done iteratively and fast. In fact, there seems little difference in the macro movement between the lower block and the upper block.
So who says that a hard style has no circular movements?
The great thing is that this move can be done automatically; it can be applied with very little thinking and can be used against many different combinations - just make sure to look at what's coming and match it to the target area!