Many stations will let us put a hold on a time slot now and pay them by the 28th. They'll call if someone else comes along with cash in hand and give us the option to put down a deposit before selling our ad slot to someone else. There are also two kinds of ads preemptible (which means your ad can get bumped out of the timeslot of program you scheduled it for if someone else comes along) and non-preemptible (which means you own a specific time slot and no one can take it away). For obvious reasons non-preemptible are more expensive, a ot more expensive. But they are the way we want to go for the Super Bowl slots that are during the game. We may throw in a few pre game slots that are preemptible because the chances of getting bumped there are pretty low.
Tell me if that doesn't answer your question.