Why is there a small hole on the top of spray-can lids?
These little holes are a good example of “a feature built into a product so that it can handle unusual or unexpected situations.” We don’t think about or see these situations in the normal use of the product. For example, if you look at the sheet metal under the hood of your car, you will see little bends in it. Those bends are placed there so that in an accident the front of the car will fold like an accordion and absorb the impact. The bends don’t do anything unless a crash occurs, and then they are very important. With a can of Pam, the lid fits very tightly so that oil won’t ooze from the nozzle down the side of the can and onto your shelf. If the manufacturer puts the caps on the cans in New Jersey and then ships the cans to Denver (the “Mile-High City”), a funny thing happens — the air pressure inside the lid pops the lid right off. So the poor stock boy at the grocery store has to put the lids back on 30 cans before he can put them on the shelf. What a pain! When the lid was pu
