Boyd’s Bible Dictionary:
(opening). A spring on boundary of Judah and Benjamin (Josh. 15:9; 18:15).
Concise Bible Dictionary:
A spring that formed the boundary of Judah and Benjamin (Josh. 15:9; Josh. 18:15). Identified by some with Ain Atan, 31° 41' N, 35° 10' E.
Jackson’s Dictionary of Scripture Proper Names:
opening