"Arnis" is an umbrella term used in the names of many different styles of Filipino martial arts, which can also be referred to as "escrima" or "kali." All of these terms refer to arts of swordsmanship and stick-fighting from the Philippines. Because there are so many different styles of Arnis, there is no single body of techniques. Each art has its own methods.
The Classical Approach
Before the modernization of teaching methods in the Filipino martial arts, there was no organized curriculum and no concern for the safety of students. In addition, many of the old Arnis masters had an attitude of reverence for the stick with which they fought, and did not wish to clash it against the opponent's stick. For this reason, the classical method of blocking in Arnis did not target the weapon but the person using it. Instead of a block as such, the Arnis master would use a counterstrike to the hand or arm, sometimes injuring their own students in the process.
The Modern Arnis Approach
In the system known as "Modern Arnis," the block is made against the opponent's weapon, a change from the method of the classical masters. The techniques are focused on blocking the attack, grabbing the opponent's stick by hand and then either taking it away or controlling it. This method of blocking is sometimes criticized, because it departs from the older attitude that the stick is not a weapon in its own right but merely a training weapon for the sword. Filipino arts that use actual swords do not apply hard blocks like those in Modern Arnis, nor do they attempt to grab the opponent's blade.
Basic Blocks of Arnis
Despite the different fighting philosophies found in different styles of Arnis, most styles use the same basic set of blocks for the simple reason that these are the areas of the body that the fighter must defend if he wishes to avoid being struck. Standard blocking techniques include a block to the inside, a block to the outside and a "roof" (or overhead) block. There is also a figure-8 pattern, which can have the effect of a block because a figure-8 strike will naturally tend to intercept an incoming attack.
"Displacement" is an alternative to simply applying hard blocks against the opposing weapon. A displacement block is actually a strike. If it is directed against an attacking weapon, it will knock it aside, thus protecting the fighter who uses it and serving the same purpose as a block. If it is directed at "vital points" or vulnerable targets on the opponent's anatomy, it has the effect of a counterstrike. Displacement is closer to the classical technique, as opposed to the impact blocking found in Modern Arnis.