These are three rings linked together in such a way that if you would take one out, the remaining two rings would be seperate. Each one goes outside one ring, and inside the other. I thought it would be a nice simple soldering exercise and also a nice surprise gift for my husband.
As always, if you think it's simple, it usually isn't... I made the mistake to make three perfectly round rings - one with a little gap of course, to assemble them - before i realised i would never be able to get three perfect circles in a Borromean configuration! All three need to be slightly elliptical for them to fit.
To assemble the rings, i made two rings somewhat elliptical, then the third ring was fiddled into place and was soldered to complete the ring. The final step was to use a tapered mandrel to get all rings as round as possible.
More rings can be found here.