Directing wireless signals and customizing wireless coverage is of great importance in residential, commercial, and industrial environments. It can improve the wireless reception quality, reduce the energy consumption, and achieve better security and privacy. To this end, we propose WiPrint, a new computational approach to control wireless coverage by mounting signal reflectors in carefully optimized shapes on wireless routers. Leveraging 3D reconstruction, fast-wave simulations in acoustics, computational optimization, and 3D fabrication, our method is low-cost, adapts to different wireless routers and physical environments, and has a far-reaching impact by interweaving computational techniques to solve key problems in wireless communication. Categories and Subject Descriptors C.2.1 [Computer-Communication Networks]: Network Architecture and Design—Wireless communication Keywords Wireless networking; 3D fabrication; Signal map; Design