http://www.techradar.com/news/revealed-aluminum-foil-can-actually-help-to-fix-wi-fi-weak-spots

It sounds like something dreamed up by the foil-hat-wearing-brigade, but new research has proved that a simple 3D printed (specially shaped) piece of plastic covered with aluminum foil can work as an effective Wi-Fi signal booster (or rather, signal director).

As you’re probably aware, most Wi-Fi routers emit a wireless signal in all directions with (more or less) equal strength, and the basic idea is to use a simple shaped reflector to better redirect the signal.