Clarifications sought: Verticality, Reaching in , High Dribble--anybody help ?

[Travelling Man]

OK, you all have been so very helpful in this regard.
As a female ref I used to be intimidated by fans shouting "high dribble" and "you better call that reach in". I would stifle my whistle and let the play proceed because I thot there was no violation occuring.
Also, thanks for the insightful comment that said "a foul can occur even if the player who is doing the boxing out shoves his body into a rebounder who has elevated behind him/her".