1.   Where a boundary line is shown as approximately following the centerline of a street or highway, a street line or highway right-of-way, this centerline, street line or right-of-way line shall be construed to be such boundary. The boundary line will be changed automatically, whenever the said centerline, street line or highway right-of- way line is changed, provided that the change does not exceed 20 feet.

2.   Where a boundary line is shown as following a lot line, such lot line shall be construed to be said boundary.

3.   Where a boundary line follows a stream, such boundary shall be deemed to be the centerline of said stream. For any lake, pond, reservoir, river, or other body of water, the regulations of the most restrictive adjacent district in which they are located shall apply.

4.   Where a boundary line is shown as approximately parallel to a street, highway, stream, or railroad line, such boundary shall be construed as being parallel thereto and at such distance from the centerline thereof as is indicated on the zoning map.

5.   Where a district boundary line divided a lot which was held in single and separate ownership, at the time the boundary line was established, the use regulations applicable to the least restricted district shall extend over the portion of the lot in the more restricted district, a distance of not more than 30 feet beyond the district boundary line.