What is this stuff?

[tiffanyharvey.livejournal.com]

With all of this creative inspiration from craftgrrl, but no money to get new supplies, I started routing through my assorted craft supplies to see what I had laying around. Well, I cam across this stuff that I remember using in elementary school, but I can't remember what it is called (did I ever really know?) or how it works ~

They are thin rectangles of plastic (these are all metallic), and I remember you can cut them out & then heat them to shape them however you want. They will re-harden in that shape. I think they were really popular for making barettes in the 80's, but I don't think you can get them anymore. What I can't remember is how to heat it... I feel like you soaked it in warm/hot water until flexible, but does anyone else out there remember this stuff?? I would love to make something up with them.