Charles Ellicott Commentary Exodus 28:26

"And thou shalt make two rings of gold, and thou shalt put them upon the two ends of the breastplate, upon the edge thereof, which is toward the side of the ephod inward." — Exodus 28:26 (ASV)

Thou shalt make two rings — that is, “two other rings.” These were to be put on the two lower corners of the breastplate, “in its border,” or at its extreme edge.