Look up the DIY parabolic reflectors people used to use on their WiFi antennas, they did actually work! I used one and recorded a marked improvement in WiFi strength at the furthest point in my home that was previously a low connection quality spot.

Radio waves come out of an antenna and just go in every direction, so a router against your outer wall is wasting a lot of its energy just directed into the neighbour’s house. If you can reflect some of that back in, you get improved signal reception. It’s very cool :-)