This is a really simple one for directing your routers wifi signal to where ever you want. Its basically installing a parabolic reflector to your routers antennas. Now, even though 802.11 signal will pass through a piece of sheet metal, the majority WILL deflect.
Step 1: Parabolic WiFi Signal Deflectors
Simply get some balsa wood or other light wood and cut out your arch for the deflectors. Then add your hole for the antenna. You will need 4 of these wood pieces. Then cut out your light sheet metal and glue to the wood. Simply place the deflectors on the antennas and rotate them in the direction you wish your signal to radiate the strongest.