Why does my coach tap the underside of my blade after I hit them in a lesson?
That little tap is a signal, and most coaches use it to say several things at once: your hit landed properly, hold your finish for a moment, and now recover. It is one of the most common habits in the fencing lesson, handed down from coach to coach, so even coaches who do it every day may give you slightly different reasons. None of them are mysterious, and knowing what the tap is checking helps you get more out of every repetition.
Here is what the tap is usually checking. First, point fixation: did your tip stay on the target and bend the blade, or bounce off and slide away? Second, your hand at the finish: in foil and épée your hand should be high enough and closing the line, so the coach's blade meets resistance instead of finding a way back to you. Third, timing: some coaches make the tap a deliberately late parry, which teaches you to finish the hit before the defense arrives and not to freeze when the other blade moves. Finally, it is a cue to recover to en garde without anyone saying 'and back' fifty times a lesson.
Watch what happens after the tap, because the recovery matters as much as the hit. Many coaches keep light pressure on your blade as you come back, and if your hand drops, your elbow flares out or your tip drifts off line, their point slides onto your arm or chest. That is the lesson: recover your distance while your blade keeps covering you, so a real opponent's riposte or remise has nowhere to land. In sabre, coaches more often snap your blade into the guard they want you to finish in.
Not every coach likes the habit. Some feel that knocking the blade up after every hit fixes the point for the student, tightens the shoulder and teaches you to wait for a signal instead of finishing on your own, so they use words or a real parry at controlled speed instead. Both approaches can work. If you are not sure what your coach wants, ask between exercises: 'When you tap my blade, what should I be checking?' Good coaches like that question, and the answer usually points straight at what they are working on with you.