Hi LL,
A "boxed" bet applies to Pick 3s Pick4s and actuall is an even more common term at the track for horse racing bets.
When I was involved in thoroughbred horse racing and breeding I would always "box" my bets. This means I cover all combinations of outcomes. ie if I am betting an exactor (first and second over the finish line on horses 7 and 9) then a "boxed" bet wins whether it is 9 and 7 or 7 and 9.
A boxed bet in Pick 3 means all combinations of the numbers all ways.