Soup cans are constructed so the lid falls in when you open them. The tiny red string on the bandage wrapper isn't connected to anything so when you pull it, it just slides out. After you do some addition, multiplication and subtraction, it tells you that you don't qualify. When you are in the checkout line at the supermarket, they open another register that only the people behind you notice. Tables and chairs are designed so when you reach under the table to retrieve something you will bang your head on the way back up.
Elevators stop at floors where nobody is waiting.