Video describes how to use conductive gaskets to seal a metal garbage can (or other ad hoc Faraday cage).

To order gaskets, see

Additional Resources:
Disaster Preparedness for EMP Attacks and Solar Storms
EMP Trash Can Faraday Cage Testing in Lab Posting.
Black Hole Faraday Bag – Standard Non-Window Size
EMP Introduction to EMP and Faraday Cages

Thank you, Charlie Romeo-04 for a heads up on this video!