Ouches of gold. "Buttons" according to one view (Cook): "sockets," according to another (Kalisch): "rosettes," according to a third (Keil). Some small ornament of open-work (see the comment on Exodus 28:11), which could be sewn on to the ephod, and whereto a chain might be attached, seems to be intended.
The object was to fasten the "breast-plate" firmly to the ephod.