In City of Webster v. Signad, Inc., 682 S.W.2d 644 (Tex. App.--Houston 1st Dist. 1984, writ ref'd n.r.e.), the court considered a vagueness challenge to a city sign ordinance that provided that any outdoor advertising signs could not be rebuilt if there was damage to "any substantial parts" of the sign. 682 S.W.2d at 645-46. The court held that the quoted phrase was fatally vague and violated due process because it did not provide operators of outdoor advertising signs with fair and adequate notice as to what sign repairs were permitted or prohibited. Id. at 647-48. The ordinance provided no definition or guidelines for measuring "substantial parts" of the sign, leaving the court to conclude that persons of common intelligence would be left to guess the ordinance's meaning. Id. at 648. While the court noted that the words "substantial parts" are common, they are not self-explanatory. Id. at 647. As the court explained, "Parts of a sign may be simultaneously 'substantial' and 'insubstantial' depending on whether the test used is economic, physical, or functional." Id. at 648. The court illustrated the uncertainty and ambiguity that arose from application of the "substantial parts" standard as follows: "If an economic test is used, how expensive must a repair be to rise to the level of "substantial"? If a sign is valued at $30,000, is $1,000 in damage "substantial"? If a physical test is considered, is damage to one pole of a five-pole sign "substantial"? Should "substantial parts" of the sign include other than structural parts? Section B(15) of the Ordinance defines a "sign structure" as "the support, uprights, bracing, and framework of any outdoor advertising sign"; sign panels, readily movable and changeable, are not defined as a part of the sign structure. Is damage to one or more sign panels therefore to be considered as damage to a "substantial" part of the sign? A sign with broken or inoperative lights is not functional during nighttime hours, although the cost of repairs is small in comparison with the sign's total cost. From a functional perspective, the lights are "substantial parts" of the sign, while from a cost perspective they are not. The same ambiguity arises in numerous similar practical considerations. . . . Operators of outdoor advertising signs receive no fair and adequate notice from section H(2) of the Ordinance as to what sign repairs are permitted or prohibited." Id.