some like to put it chest high of ur boxing stance. so itll simulate a boxers head avoiding ur punches.

some likes it really stiff so it wont move around that much but then again it wont simulate a boxers head if it doesnt move that much. i guess u can loosen it up so u can simulate head hunting and so u can avoid the ball when it rebounds towards you or tighten it so u can train to punch quicker.