‘ From Tappuah the border went along westward to the brook of Kanah, and its goings out were at the sea. This is the inheritance of the tribe of the children of Ephraim according to their families, together with the cities which were separated for the children of Ephraim in the midst of the inheritance of the children of Manasseh, all the cities with their villages.'
The line from Michmethath to Tappuah is not mentioned but assumed (compare Joshua 17:7-9). The author had many surveyor's records and reports to select from, many probably made on Joshua's campaigns, and he did so to present a certain picture without too much repetition. Tappuah (meaning ‘quince') is possibly modern Sheikh Abu Zarad, about twelve kilometres (eight miles) south of Shechem. Its Canaanite king was defeated by Joshua (Joshua 12:17) but nothing is said about the actual town. The Wadi Qanah ran west from the watershed at the head of the Michmethath valley, eight kilometres (five miles) south west of Shechem. This was its lower course which ran on to the Great Sea.
“This is the inheritance of the tribe of the children of Ephraim according to their families.” These are the technical descriptions that finish off the allotment to each of the twelve tribes apart from Levi, whose inheritance was YHWH, and Manasseh who were counted with Ephraim, indicating the early date of the descriptions (see on Joshua 15:20). Note that Ephraim and Manasseh were conjoined in that Ephraim had cities within Manasseh indicating joint rule.
“Together with the cities which were separated for the children of Ephraim in the midst of the inheritance of the children of Manasseh.” We are not told why this was so. Possibly it occurred through Ephraimite assistance to Manasseh at an early point, but it confirms the oneness between them and suggests combined rule to some extent.