I use a wallet with a money clip on the outside. The money clip uses two magnets to hold the folded dollah bills together. The two magnets both have a north and a south pole, and both magnets exert a field. Due to the magnetic fields, the two magnets are attracted to one another. The people who made the wallet had to make sure that the two magnets aligned so that opposite poles come in contact, otherwise the money clip would not work. If the two south poles were facing each other or the two north poles, the two magnets would repel each other and serve no purpose. Sometimes, if i lean against something metal, my wallet is attracted to it and pulls my pants out to stick to the metal. The metal has to be iron, nickel, or cobalt in order for my wallet to do this to my pants, and it is really quite annoying.