Exodus 28:25 says
And thou shalt make upon the breastplate two rings of gold, and shalt put the two rings on the two ends of the breastplate. And thou shalt put the two wreathen chains of gold on the two rings at the ends of the breastplate. And the other two ends of the two wreathen chains thou shalt put on the two settings, and put them on the shoulder-pieces of the ephod, in the forepart thereof.
From the text it is evident that the chains are meant to connect to the rings in the breastplate, and to be affixed to the Shoham stone's settings that were on the shoulder straps of the High Priest's apron. However, Gd doesn't elaborate in the text about how the chains were attached to the settings, as opposed to every other attachment of the breastplate to the apron, which was done by way of rings. I looked in Rashi on these verses as well, but he does not explain this detail any more clearly, from what I can tell.
How were the chains attached to the Shoham settings? were they soldered together? Were there unmentioned rings?
Please source your answers!