Florin from YouriTronics have taken a video where he shows how to make very simple WiFi signal reflector and this way increase the signal level to one direction. For this he used soda can cut in half. Probably everybody know parabolic antennas and ho do they reflect signal from focal point. If WiFi antenna is placed along can shape focal point, the signal waves will be directed to one direction. Of course soda can isn’t parabolic shape, but this cheap solution gives noticeable results.