Answer:
For guys lacrosse, the ball cannot be below the sidewall at the very bottom. If it is, its illegal. So the head itself has a sidewall, and the lowest point on it is where the ball cannot below (depth-wise). Also, is you hold your stick straight up with a ball in it, and keep tilting is so the pocket would be upside down and the ball doesn't come out when its upside down, it's illegal. And if you put a ball in your pocket and tilt it so the scoop is parallel with the ground (about a 90 degree angle if touching the ground) and the ball doesn't come out then it's illegal. Also, you cannot have any rips in the mesh.