|English||to constrain (verb)|
Constraining in Capo Ferro's language is the act of placing your sword or body in such a position as to restrict your opponent's offensive options, forcing them to act (take a tempo) in order to return to a position of threat or launch an attack.  This action is done as you arrive at wide measure and is maintained all the way to the point of striking.
When the opponent's sword is not in a threatening position, for example it is pointing offline, you must only constrain the body. This means to constrain only the distance.
Constraining the Sword
To fully constrain the sword, one must do three things:
- Turn their true edge towards it.
- Have superior leverage.
- Cross over top of their sword with your own (Crossing the Line).
A partial, less covered constraining of the sword could also be performed simply by cross the line of the opponent's sword. This is seen in the intelligent play of plate 15 where our fencer initially attempts a strike in second, presenting his false edge instead of his true edge to the opponent's weapon, by cross the line with the false edge, our fencer is then able to To gain the opponent's weapon by rolling back to the true edge for the final strike.
Turning the True Edge
In the act of constraining, the true edge is turned fully or partially towards the opponents weapon. Generally it is better form to turn the edge only part way, leaving one half way between third and second for example. This half-turning facilitates a faster turning of the edge to the opposite side if the opponent disengages to strike.
- Why? The geometry of the human forearm, wrist, and hand is such that the blade of the sword extends not from the center of the arm's cross section (the way one's middle finger does), but rather from the side (sort of the way your thumb does). This means that the mass of the sword is off the center-axis of the arm, so that one side of the arm is better defended by the sword than the other. The better defended side is the side that your fingers are on, which is the same as the direction in which your knuckles point, which is the same as the direction in which the true edge points. Therefore, the side towards which you point your true edge will be the better-defended side. NEED A PICTURE.
Acquiring Superior Leverage
To have superior leverage you must ensure that your opponent's blade is closer to your strong than your blade is to their [strong]]. Capo Ferro states that you should have greater leverage by a distance of one palmo. 
- Why? In a lever (like a sword's blade), torque increases proportionally with the distance from the pivot point (e.g. the hand) to the point of application of force (e.g. the place where two swords cross). When two fencers press on one another's blades, they are applying torques to counter the torque applied by their opponent's sword. Assuming opponents who can apply equal torques to their blades, the one who has to resist a more distant force must resist a greater torque, and will therefore lose the battle.
- Why? Two disasters may occur if one ignores this rule: first, the opponent's point is dangerously close to the fencer's hand when the fencer is applying his forte; second, the fencer gives the opponent the opportunity to make a very small disengage.
Crossing the Line
Capo Ferro describes this principal in plate 15, when he advises the fencer to point towards the right shoulder when approaching on the inside and to the left shoulder when approaching on the outside.  This directing of the blade causes it to cross over top of the opponents blade creating an angle that provides a physics advantage. Capo Ferro also states that when presented with an opponent's sword in a straight line (i.e. pointing directly at you), cross it with an oblique line (as described above) and when presented with an oblique line (i.e. the guard held on the right, the point on the left) cross it with your sword in a straight line.  Both of these scenarios present a situation where your sword crosses over top of the opponents sword.
Crossing provides cover of the opponent's sword by channeling their blade into the strong of yours as they apply pressure. This is the most critical of all the advantages, however Capo Ferro makes no such reference.
- Why? The simple reason is that, from a standpoint of body mechanics, it's easier to apply a downward force than an upward force. However, there is an additional reason: having a position with the advantage of leverage (see above) is good, but no configuration remains static. The situation in which swords are engaged and each fencer is applying force to the other's sword is analogous to ball sitting on a sloped surface, where the weight of the ball is the sum of the total force applied by both fencers. Just as the ball will roll downhill, the weaker sword will slide "downhill". Depending on the stronger sword's orientation, this can either be towards that sword's point or towards its guard. When the stronger sword is crossed over the weaker, "downhill" is "towards the guard".
Constraining the Body
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Gaining the Sword
To gain the sword is to penetrate the opponent's defense, having found their sword, and thus amplifying the strength of your finding and drive their sword off the line.
There are three essential features ("the fencer refers to the one who gained the other's sword):
- The point of crossing moves deeper into the fencer's forte, increasing leverage.
- The true edge of the fencer's sword drives the opponent's blade further off line at an increasingly large angle.
- Any blade action made by the opponent to escape the constrained position is matched by a blade action of the fencer, so as to maintain the constraint.
Rules of thumb
In addition to these essentials, there are two other rules of thumb that make gaining safer and surer.
- "The rule of the palmo": the fencer should ensure that the point of crossing is no closer to the opponent's point than one palmo. This ensures that at least a small tempo is required for the opponent to disengage, and protects the fencer's hand from strikes through the hilt.
- "Striking according to the point": the fencer should aim at least as high as the point of the opponent's sword, traced directly back to the opponent; e.g., if the opponent's point is at his chest level, the fencer should strike to the chest or above. This ensures that the fencer's sword does not come too close to the opponent's forte.
Difference between stringere, finding, gaining
Stringere is a tactical relationship among all elements of the fight (the two fencers, their blades, the measure, the tempo, and the lines). Gaining is a purely mechanical interaction between blades. A fencer may stringer his opponent's sword without touching it, and may do so in any measure. Finding the sword is a geometrical relationship between the blades, and usually refers to the action of acquiring that relationship (after that action has taken place, we may say that the opponent's sword is "found"). Finding the sword does not, in principle, require blade contact; gaining is always a continuous action and always implies blade contact.
- Do we want to have this article as "To constrain" or as "Constraining".
- Do we want to classify these articles in some way as "technique definitions" "word definitions" etc?