Bought these to hold the calender on the side of the fridge. Side of refridgerator is the 'painted grooved metal' so everything just slides off. You can literally pull the calender out of the clip and the clip is in the same spot. Didn't think that was possible. I bought a second pack for artwork.
These clips lasts forever and hold more than one sheet of chart paper at once (I use two clips one at each side to hold 3 or 4 sheets that I need to keep together). I use them to hold up charts on my classroom eraser board and they are extremely strong and easy to use. I have 9 of them now and I'm sure I'll buy more. Don't waste time and money on smaller less powerful magnets that cause your posters to slip and slide. Get these and everything will stay right where you left it.