The name says it.
I took about 6" of grey duct tape and layed it on an old 2-4 cut around an old Duncan friction sticker with a hobby knife. They are GREAT!!! :o 1 sticker=nonresponsive 2stickers= responsive.
They are a little time consuming but when y0ou think about the money you are saving it all becomes okay. ;D Try it and see what you think I put 1 in my freehand.