What is the meaning of "v'Sa'ar ha'Gevul"?
Malbim: It surrounded the mountain on three sides.
What is the meaning of "v'Nasav li'F'as Yam Negbah"?
Rashi: [Atros Adar was the northwest corner of the border. From there] it turned to the south.
Where was Kiryas Ye'arim?
Malbim (19:1): It is half the length of Eretz Yisrael [from east to west].