TgJ Jos18:16 :וְנָחֵית תְחוּמָא לִסטַר טוּרָא דְעַל אַפֵי חִלַת בַר הִנֹם‏ : the border descends to the side of the mountain that faces the valley of the sons of Hinom
See the entire entry for lsṭr prep. beside