The grade line from one corner of a block to the next corner of the same block shall be of uniform slope, ascending and descending, and the grade of all lots may be determined by a straight line running along the boundary line of the block from one corner to the other at the grade above indicated at such corner, except that where a different grade is established at an intermediate point on the boundary line of certain blocks as appears above, the grade of any intermediate point along the boundary line drawn from the corner of such block at the grade above indicated to the nearest grade point established as aforesaid.
(Prior Code, § 2.0203)