Stop throwing at once if someone approaches your exercise area!
Sometimes, the knives bounce back from the target and could injure people. Thus always watch the knives. And if it's not your turn, or you are just having a conversation in the same area - watch the knives!
Spectators and bystanders are welcome - if they are at least 3-4 meters behind you. The best solution is a line on the ground or something 3 Meters behind you that nobody must overstep. Nobody must be closer to the target than you.
Never throw at people or animals! Don`t even aim at them as a joke. Knifethrowing is a sport!