This paper must be shown at the start of each stage.

Received at registration, and if you lose it, they will not give you another one.

The 2 key pieces of information:

1 – proof you passed breathalyzer that morning
2 – the weight of your car before the race. It is weighed again at the end, and if it doesn’t match*, disqualification
* because a mismatched weight implies you added enhancements, swapped the engine, some sort of cheating may be happening.