International 505 champion Peter Alarie explains this concept by thinking of clear lanes as numbered in order of desirability. The lead boat is going to take lane No. 1. The number one lane may be right on the shift or on the layline. To keep its air clear, the second boat will take lane No. 2, to leeward of No. 1. The third boat will take No. 3 and so it goes down the line for all the boats that are close enough to affect your air. If you’re in fourth position, you can’t tack in lane No. 3. If you try, you’ll end up in bad air.