People go through a lot of cereal—and my family is no exception—but if there’s one thing that drives me a little nuts, it’s that flimsy cardboard tab on the top of every cereal box.

Cut two openings in the cereal box top – one on each side of the part of the box with the tab that is used to close it. Cover one of the openings with a piece of foil.

Then fold one of the long flaps so that it's also inside the cereal box. Next, working with one of the short sides, pinch the ...