Alex Rudick, 2, has lots of toys, but all he needs to keep him busy is a door. "He'll spend an hour opening and shutting it," says his dad, Jon, of Washington, DC. "He finds it absolutely fascinating."

So do a lot of other toddlers. While it may seem like they're just making noise by opening and closing a door, drawer, or container, they're learning more than you think: how objects work, the sounds they make, and the basic concepts of "open" and "closed," says Tovah Klein, Ph.D., director of Barnard College's Center for Toddler Development in New York. It also helps them understand the idea of separation  -- the idea that things that go away come back.

To pass through this phase safely (and sanely):

For a thrill with less noise, give your toddler some toys and household items that open and close quietly, such as a shape-sorting box, a play refrigerator, or Tupperware with lids.

Protect little fingers by putting a foam stopper around door frames.

Remove or lock up any unsafe items in drawers and cabinets. Instead, fill them with things that can be played with, like wooden utensils and pots and pans. You never know  -- while he's indulging in his new favorite pastime, you may find the time to whip up dinner.