Powerful neodymium magnets with adhesive. We recommend the self-adhesive magnetic discs and blocks to stick the magnets on any surface. The adhesive we use on our magnets is 3M.
Arranged by pairs in strips (1 north pole and 1 south pole with adhesive surface)
Different shapes: round or square
An alternative are flexible adhesive magnets but their clamping force is much lower. Sen appropriate to fix photos or notes in a refrigerator or whiteboard.