Many geocachers would like to use magnets to attach micros (small film canisters containing log book and pen) under bridges, guard rails or other metal hiding spots. Please keep in mind that magnets are not designed for outdoor use because tmagnets will eventually rust.
Therefore it is important to protect the magnets well if they are attached to the outside of the micro. We recommend, however, to put the magnet on the inside of the micro to protect it from corrosion and blows.
Magnets are good bartering objects for larger caches that are not attached to anything with magnets. We recommend raw magnets in their original packaging (plastic bag), since this protects them from corrosion.