A simple solution for a back-breaking problem! Don't haul crates of balls on and off the field any longer.
The baseball Crate Mate by Muhl is designed to carry baseballs or softballs in standard square milk crates. The Crate Mate will hold 3 crates firmly in place in the bottom storage area, plus, the top adjustable platform could carry a fourth and be used to hold a crate of balls for batting practice.
Optionally add 3 crates to your order (additional charges apply).