Once you’ve set up the frame and roof of this playhouse, your job as contractor is done — and your job as supervisor begins. Turn your kids loose with a battery-powered drill (it’s safe) to install the more than 25 play panels that form the walls (and windows and doors and a mail slot) of the house in whatever combination they want. The screws are built into each of the panels, so your kids won’t lose or swallow them. It’s easy to unscrew and reattach panels, so you can perpetually redesign and remake their playhouse however they want to.