Why is jacking up a car different at a rally?

The big issue is that you often are servicing somewhere that isn't a paved or concrete surface. Let's jump immediately to the worst case scenario, a grass field. There are two problems here:

1. The jack stands sink into the ground, which can lead to the car falling off the jack stands.
2. When jacking up the car via the front or rear diff with a big floor jack, the large roller directly under the weight bearing pad isn't free to roll because it digs a groove into the ground. So as you're jacking the car up, you're also actually pulling it toward you. This can lead to the other end of the car tipping its jack stands over.

The first problem is solved by putting pads or plates under the jacks. Using four blocks of 3/4" plywood, twelve inches on each side, will get this job done. Under the front, sliding a piece of aluminum under there while raising the front section solves the second problem.