Here's a YouTube tutorial on a quick and dirty way to use aluminium foil, a template and some glue to make a Wi-Fi extender. As a bonus, it looks like a tin foil sail, and it's called a Windsurfer. Slightly better than a Pringles can, yeah? :) They use a printout of a template for the which comes from the Free Antennas website.
How to make a Wi-Fi extender [DL.TV]