Shen was a tooth-pointed or sharp-pointed rock (see 1 Samuel 14:4), nowhere else mentioned and not identified.
Related Commentaries of 1 Samuel 7:12
1 Samuel 7:12
12 Then Samuel took a stone, and set it between Mizpeh and Shen, and called the name of it Ebenezer,c saying, Hitherto hath the LORD helped us.