This is a "Red Devil" paint masking tool. These things are GREAT. They are very thin, but they have a slight curve that gives them strength. They can be cut into various triangle shapes and work very well for holding the flaps back while tucking roll downs, or pressing out a pesky corner in a quarter pane. The only problem is, I can't find them anymore! They have been replaced by a thin aluminum version, which I'm sure works great for it's intended purpose, but they are now useless for tinting.