one of the things World Challenge racing has is a tire rule. Competitors must start the race on the tires they qualified on. sometimes we have tire rules in club racing too -- Formula Ford used to have one, and one was just instituted for Spec Racer Ford within the couple of weeks.
when there's a tire rule, there is a requirement that tech mark tires. in club, frequently we just
walk through the grid before qualifying with a can of spray paint and a template of some kind. for world challenge, the competitors bring the chosen set of tires to tech, where they are marked with the car number and class (at lime rock, this was being handled by a group led by my old friend George Wolfstirn, who is actually the first tech chief i ever worked for back in the early 90s.)
after the first qualifying session, it is then tech's duty to walk the pregrid for any additional qualifying sessions, and walk the pregrid before the race, checking to make sure the right tires are on the right car. normally the competitors are allowed to change one tire as a freebie; at a place like lime rock that absolutely kills left front tires, this can be pretty important.