Although Banksy was unaware of his participation, he and I collaborated on this college. The rat image was unearthed from some papers I brought back from the UK and my contribution was the rubbing on the right hand side which was from a metal plate in the sidewalk in front of our flat. The street art materials just worked together.
Rubbings, or frottage in artspeak, are an excellent way to record plaques, manhole covers, gates, doorknobs and assorted metal street features wherever you happen to be. Materials are simple and inexpensive: crayons unwrapped and sturdy paper and a roll of tape. If you want professional materials purchase rubbing discs from art supply stores that sell them for grave rubbings. Most papers will work but some will tear here and there. Avoid this issue by buying mulberry or rice papers that are thin but very durable. Simply tape the paper to the object and run the crayon or disc over the image. Brings back the kindergarten days of making rubbings of coins.
Use the papers for backgrounds for paintings or use them in collage. The Asian papers glue down easily with minimal wrinkling.
Make yourself a small travel kit when you go on holiday and you will be able to return with unique souvenirs as well as art materials.