John, I probably should have equated my echelon info more to what he did.
As concerning a wheeled vehicle:
1st echelon: That car of yours belongs to you. You check the tires for air. You check the brakes, the engine oil, the amount of gas. How clean it is, etc. You really do not have a tool box to work on the car.
2nd echelon: The oil looked a little funny. The 2nd echelon guys actually have a tool box with real tools, unlike you. The might drain the oil to see what it looks like and even pull the oil pan to take a look inside. The have things like brake shoes, tires, oil/air filters, etc.
3rd echelon: They have a much larger tool box. One that contains items such as drill presses, maybe a lathe. They can actually tear the whole engine down and have a look at it. Pull the heads and torque them back down. They can probably do a pretty good rebuild of the vehicle.
4th echelon: The body work is messed up. Major components need to be replaced. 3rd might have been able to do an engine rebuild but not have been able to handle transmissions and differentials. 4th has a very large tool box with large presses, overhead cranes, etc.
5th echelon: again, factory maint. The frame is bent. The vehicle was submerged. A total end to end project must be done.
One of the big places that 4th (and 5th) echelon maint is done today is at Tobyhanna Army Depot or TOAD (or called frog by insiders). TOAD is capable of all 4th echelon maint and has many civilian contracted units located there which can perform 5th echelon.