Twins cracking each other up

Philippa's tall enough to open all the doors in the house now. That means I can't lock her in the playroom anymore or out of her parents' office. I look away for a second and she's gone. And when I'm in my room I keep hearing someone messing with the (very hard to open) door at the top of the cold, steep, winding staircase. But they're going to Kindergarten in 2 weeks!