I have the same problem. The post-its work on one of my machines but fall off of the other ones (i hnow have four that I use). I put double sided repositionable tape the machine and put a note with the needle info in it. sometimes the tape is labeled "poster tape" Its non-permanent, sort of like post-its only stronger. When I remove the needle I remove the note too and the tape stays on the machine for the next time. Then I poke the needle through the note with its info on it and put it in a the tray with all of my needles. When the tape looses its sticking power or gets dirty, it comes off with no residue and I put on another piece. I use this for notes about stitch settings when I use decorative stitches too..I can never remember how wide or long I made them.