these toolboxes were equipped with small wheels that were designed to roll over flat surfaces and they worked really well but the only problem with that was during my deployment to Afghanistan there were few places that were flat or smooth enough to roll the heavy toolbox on trust me we tried. it was more like dragging an anchor behind you plowing a path through gravel which inevitably broke the small wheels so I had a plan.
Step 1: These Wheels Were Bolted on As an Accessory
they were easy to take off and store in the toolbox to be installed later when you have to turn the toolbox back in once the deployment was finished
Step 2: I'm Sorry I Don't Have Pictures Building the Dolly But I Have a Few of the Finished Product
I started off with scrap grounding stakes and an axle with inflatable tires from a robinair air conditioner most mechanics use to refill the oil and air-conditioning gasses in a vehicle.
I took the handle and existing wheels off and bolted on some brackets from a universal led light kit we used for our military vehicles then bent the grounding stakes and welded them to the robinair axle as well as welding a bracket to be bolted into the existing holes where the handle goes on the top. the bottom end I welded on pipe to fit in between the brackets at the bottom so a bolt can go through and be securely bolted to the toolbox
Step 3: No More Dragging
it worked very well after the modification and it saved a lot of headache. and after a while a lot of the small wheels on the other toolboxes ended up breaking from being pulled over the gravel over time.