BJ's membership warehouse (not sure if they're still around) had a system which not only weighed the items, but also had a "gate" made of infrared LEDs your pur

BJ's membership warehouse (not sure if they're still around) had a system which not only weighed the items, but also had a "gate" made of infrared LEDs your purchases had to go through (which presumably checked their height). If you bought a book or something else too thin to activate it, the belt would back up and force you to scan again. I hated it with a passion, and when Costco opened in town, I immediately moved my membership there.