At a crowded repair desk, everyone wants the next available technician. A queue lets people stop continually competing for attention. Once their place is recognized, they can expect service after those ahead of them.
The line can be physical or recorded through numbered tickets. Wimbledon uses numbered, nontransferable queue cards to make waiting order explicit. The rule becomes something staff and participants can both refer to.
Waiting is a kind of price
Imagine two people who each need a fifteen-minute repair. One has a free afternoon; the other must return to a shift in half an hour. Equal places in a first-come queue do not impose equal burdens. Waiting uses time, mobility, and flexibility that people possess in different amounts.
A ticket system may let someone sit down or leave briefly, changing the practical cost without changing their order. Priority access for urgent needs changes the ordering principle itself. Both can be reasonable, but people need to understand which promise the queue makes.
A queue's quiet achievement is preventing every service encounter from becoming a negotiation. Its limit is that arriving first answers one allocation question, not every question about need, fairness, or efficient use of the resource.