When you cock your crossbow mark the string so you have a point of reference every time.
He has the string marked and he gets back to the same spot (atleast as close as he can without a cocking device.)
i use both the 4" and 2.25" quickspins for my cross bow.
the 2.25 are for mechanical heads only. fantastic results from both.
Cool, I might have to steal a couple of bolts and fletch them up and see how it works for him.