That reminds me..when I was a test proctor, testing was held from 8:00 a.m. - 3:00 p.m, with the last available test start time being 12:00. They were IT certification tests, and some of them took a few hours to take. I had to start telling people that they could not come in to take a test at 2:50, because testing was supposed to be *finished* by 3:00 p.m. We had posted available times for tests, and none of those start times was after 12:00. Yet, people would still come in to the test center to try and take a test 10 minutes before the test center closed for the day. Outside testers had to schedule their test online, but we allowed our students to "walk in" to see if there was an available seat for them without a prior appointment, as long as they understood that just showing up didn't mean they'd get to take the test and it was better to schedule it ahead of time, and if they turned up after the last available test time they would not be allowed to take their test.
We'd also have students schedule a test for 12:00 and then stroll in at 2:00, thinking they'd figured out a way to "beat" the rules. All that did was cause their voucher to get voided. If a test wasn't cancelled before the scheduled start time, the voucher was used regardless, and at $200 per voucher it was in their best interest to show up. Students got one voucher per certification as part of their tuition. If they failed a test or voided their voucher by not showing up, they had to pay for a new one.