For the purpose of this chapter, the Borough of Pleasant Hills is hereby divided into classes of districts which will be designated as follows:

The boundaries of said Districts shall be shown upon the Zoning Map. The Zoning Map shall be kept on file at the office of the Borough of Pleasant Hills and shall be available for public examination at such office during the hours it is open for business, except that such Zoning Map may be removed from such office for an official change or for reproduction purposes only.

The boundaries between districts are, unless otherwise indicated, on either the center line of streets, roads, alleys, or railroad rights-of-way, or such lines extended or lines parallel thereto or on the side or rear lines of lots or unsubdivided acreage. Where figures are shown on the Zoning Map between a street, alley, road or railroad right-of-way, and a district boundary line, they indicate that the district boundary line runs parallel to the street, road, alley or railroad right-of-way at a distance therefrom equivalent to the number of feet so indicated.