Magnetic sleeves are widely used in offices. People use a magnetic rubber sleeve to display some public documents, or to post some guidance notes. The plastic film protects the file from being damaged, and the magnetic strips around it are used to seal the four edges of the rubber sleeve.
Because the magnetic strips around the sleeve are mate magnetized, so when put the A side onto the B side, it will have a strong force when N pole to S pole.
This kind of magnetic sleeve is very easy to use, when you exchange the inside paper just need 2 steps, take the surface part, then click it after put the new paper in.