All billboards hereafter erected or constructed in the city shall comply with the following specifications:
(A) All billboards shall be built of shiplap, flooring or other materials as may be approved by the Building Inspector, with the face of billboards to be dressed and boards to be built upright.
(B) All posts shall be not less than four inches by four inches and not more than seven feet apart.
(C) Posts shall be planted in the ground to a depth of at least four feet. All billboards shall be firmly braced in the rear.
(`90 Code, § 5-28)