The foil has a flexible rectangular blade, approximately 35 inches in length, weighing less than one pound. Points are scored with the tip of the blade and must land within the torso of the body.
 

The valid target area in foil is the torso, from the shoulders to the groin, front and back. It does not include the arms, neck, head and legs. The foil fencer’s uniform includes a metallic vest (called a lamé) which covers the valid target area, .  A small, spring-loaded tip is attached to the point of the foil and is connected to a wire inside the blade. The fencer wears a body cord inside his uniform which connects the foil to a reel wire which is connected to the scoring machine.  When an opponent’s tip hits this vest, the tip depresses and completes an electrical circuit. This sets off a light and a buzzer on the scoring machine against the one who is hit. A colored light signifies that the valid target (the metallic vest) was hit; a white light signifies that the hit landed outside the target area. When a light comes on, the referee halts the bout — even though no point is awarded for an of-target hit. If colored lights go on for both fencers, the referee must decide who gets the point based on “right of way.”
 

Foil fencing is “conventional”, meaning that it is subject to strict rules of right of way as to when one may attack and when one should defend. These conventions extend back four centuries and continue to make foil a fascinating pursuit today.
 

The goal of standard foil fencing is to score touches on the opponent’s valid target area within the context of the right of way.

What foil fencing looks like:

Check out épée fencing here