It shall be unlawful to deposit on any public sidewalk any material that may be harmful to the pavement thereof, or any waste material, or any glass or other articles which might cause injury to persons, animals or property. Merchandise or other articles may be deposited on sidewalks preparatory to delivery; provided, that the usable width of the sidewalk is not thereby reduced to less than four feet; and provided, that no such article shall remain on such walk for more than one-half hour. (Ord. 64 § 25, 1961)