Exodus 39:19-23

They made two gold rings and placed them on the two ends of the breastpiece, on its inner edge which was next to the ephod.

Furthermore, they made two gold rings and placed them on the bottom of the two shoulder pieces of the ephod, on the front of it, close to the place where it joined, above the woven band of the ephod.

And they bound the breastpiece by its rings to the rings of the ephod with a violet cord, so that it would be on the woven band of the ephod, and that the breastpiece would not come loose from the ephod, just as the Lord had commanded Moses.

Then he made the robe of the ephod of woven work, all of violet;

and the opening of the robe was at the top in the center, as the opening of a coat of mail, with a binding all around its opening, so that it would not be torn.