“How do you do that?” It’s the question Uli Kirchler hears most often when people see his intricate castles suddenly popping up from pieces of burl wood with a flip of a wrist. Many assume advanced tools — lasers or 3D printing — must be at work. But Kirchler credits the scroll saw, invented hundreds of years ago. Cutting the castles is a precise dance of angles and friction. He uses a scroll saw to cut several conical wedges that nest within themselves. When the tapered castle pieces fly up, friction holds them in place. “It makes me smile a little bit because friction in this case just makes life run so smoothly,” Kirchler says.