Some estate sales in the DC area put out a box with laminated cards with numbers before the sale begins. When you arrive, you grab a number. That lets you sit in your car. The etiquette is that folks will line up in that sequence just before the sale starts, and be let in in small groups.
I'll try to explain a nuance - If you're not there when you're number's called (they tend to call and let in groups of say, 10 at a time), you lose your spot. There were some dealers who would drive around and pick up numbers at several sales, and then go from sale to sale once they opened, and expect to be let in if they had a lower number than the next group at the door, even if the dealer's number had already been called. That meant that they expected a quick drive-by to pick up a number at 5 am would permit them to get in before someone who'd been standing since 6 am but had a higher number. Most of the sales agents have been politely telling those folks "Sorry, but that number was already called and you weren't here". That seems fair to me - it works at the deli counter.
I'll try to explain a nuance - If you're not there when you're number's called (they tend to call and let in groups of say, 10 at a time), you lose your spot. There were some dealers who would drive around and pick up numbers at several sales, and then go from sale to sale once they opened, and expect to be let in if they had a lower number than the next group at the door, even if the dealer's number had already been called. That meant that they expected a quick drive-by to pick up a number at 5 am would permit them to get in before someone who'd been standing since 6 am but had a higher number. Most of the sales agents have been politely telling those folks "Sorry, but that number was already called and you weren't here". That seems fair to me - it works at the deli counter.