U shape magnets come with a keeper bar…. time to google… 🙂
Magnetic Circuit
A magnetic field holds its strength best when the entire magnetic loop, or circuit, passes through a ferromagnetic metal at all points. A horseshoe magnet has an air gap between its two poles; the keeper closes this gap. A bar magnet, left by itself, will lose its strength over several months. Though a bar magnet has no “keeper,” if you lay two bars side by side, with the north pole of one touching the south pole of the other, they form a magnetic loop in iron and preserve the strength of both magnets.
Joining AOMCI has priviledges 🙂
