John Gill Commentary Exodus 28:23

"And thou shalt make upon the breastplate two rings of gold, and shalt put the two rings on the two ends of the breastplate." — Exodus 28:23 (ASV)

And you shall make upon the breastplate two rings of gold ,
&c.] On the upper part of it, above, toward the two shoulder pieces of the ephod; these were to put one end of the chains into previously mentioned:

and shall put the two rings on the two ends of the breastplate ;
the two upper ends or corners of it, the right and left.