I worked plant maintenance in a textile mill for 10 years. Every mechanic in the company ordered tools and boxes through Sears and payroll deduction plan. Anyway... plant maintenance required dragging your tool box all over any and all terrains. I learned why everyones box had a additional angle iron and flat iron frame welded on before my shinny new box arrived.
Burning that pretty red paint in stick welding a reinforcing frame and heavier duty casters on it, fresh outa the cardboard, really sucked but... without it the box was going to warp so that the drawers wouldn't slide. Tool weight isn't their only enemy.
