The border went out from Tappuah westward. This would seem to be a more minute description of the border line drawn from the sea to Michmethah above. Tappuah seems to have been near Mich-methah, and on the border (Joshua 17:8) of Manasseh.
According to Knobel, Tappuah signifies plain, which is a little inconsistent with his idea that Michmethah, close by, was the watershed. Tappuah elsewhere signifies apple. Unto the river Trench. The winter-bound torrent Kanah, so named from its reeds and canes, formed the border between Ephraim and Manasseh.
And the goings out (literally, extremities) thereof were at the sea This is the only possible interpretation of the passage, in spite of the obscurity caused by the same word being used for "sea" and "west."