Exodus 39:17

39:17 They attached the two gold chains to the two rings at the ends of the breastpiece;

Exodus 39:21

39:21 They tied the breastpiece by its rings to the rings of the ephod by blue cord, so that it was above the waistband of the ephod, so that the breastpiece would not be loose from the ephod, just as the Lord had commanded Moses.