In the day, before offshore, the Stardust created the line, early in the day, by posting numbers and allowed bettors, who were required to play a minimum amount, (I think it was $500), to put their names into a "lottery". The names were blindly pulled and announced which window you were to line up at and in which position. Example: Bill, window number 4, position 3.
As the wagers were placed the super would monitor and adjust the numbers as the money came in. The lines would move fast and after everyone was finished the windows would then be open to all. After all the dust settled, this final adjusted line became the "Stardust Line". Shops around town would use this to set up their own. There were a lot of opinionted lines back then and much variance from shop to shop. Runners would routinely be stationed at each to report any move.
I know this is true, at least for baseball, because I participated in it.