Speaking of single-sided magnets, we must think of one side is magnetic, non-magnetic side .This idea is wrong.
In the magnets industry, the one-sided magnet is one side of the larger magnetic side smaller magnetic force. The principle of single-sided magnet is to add a iron cover by a magnetic core, so that the magnetic force of the back of the magnet is reflected to the front, the magnetic force of the back is shielded by the iron cover, causing the magnetic force to be refracted to the front surface, thereby increasing the magnetic force on the front surface. The opposite magnetic force will still be there, but the magnetic force is slightly smaller. This evolved single-sided magnets.