The two shoulder-pieces were two parts of the ephod going up from the body of the ephod, the one before, the other behind, which when the priest had put over his head, were tied together, and covered the priest's shoulders, and part of his back and breast.
Related Commentaries of Exodus 28:7
Exodus 28:7
7 It shall have the two shoulderpieces thereof joined at the two edges thereof; and so it shall be joined together.