The set of hand signals used by the director
of a fencing bout
to communicate his decisions to the fencers and any spectators. People call it semaphore because if you don’t know what you are looking at, it can be extremely hard to follow. It is really quite simple, though.
(In every bout, one fencer is on the left of the referee, one is on the right. Such expressions as "touch from the left" mean simply that the fencer on the left of the referee scored. Also, obviously, the signal for "touch from the left" can be switched to mean "touch from the right" by switching right and left in the description.)
If you are a director trying to signify:
A touch from the left:
Raise your left hand, and extend your right hand to the right. It looks like an L laid on its side.
Extend both arms outward (to either side), then raise both hands.
Extend a hand towards either fencer, then bring them inward. Like "no touch", but just the hands move, beckoning each fencer towards the other.
Put one hand down, extend the other forward.
Point for the left!
Raise your left hand.
Attack from left
Extend your right hand to the right. (It can be seen that the signal for a successful touch is the "point" and "attack" signals just put together.)
Extend your hands to either side, then sweep both arms across. Like the "safe" sign in baseball.
Those are the major ones. As a stupid, tall, lazy fencer, I may be missing some of the more right of way related signs, but this will allow you to direct at least the best of the three weapons.