On any corner lot in any district except the B-4, no planting shall be placed or maintained and no fence, building, wall, or other structure shall be constructed at any point between a height of two and a half feet and ten feet above the upper face of the nearest curb (or street center line if no curb exists) and within the triangular area bounded on two sides by the street right-of-way lines and on the third side by a straight line connecting points on the two street right-of-way lines as required by the site triangular and vertical vision clearance illustration. However, poles and support structures less than twelve (12) inches in diameter may be permitted in such areas.