Contractors' signs: signs of contractors, architects, engineers,
builders, mechanics or other artisans performing work on a property
provided that the size of such sign shall not exceed 12 square feet,
not more than one sign for each such contractor, architect, builder,
mechanic or other artisan shall be erected on any one property, and
that such signs shall be removed within five days after the completion
of work. For projects containing more than 20,000 square feet of floor
area and where four or more contractors or trades are involved, a
single sign may be displayed advertising all participants up to a
maximum of 64 square feet. If the larger, multiple listing sign is
used, smaller individual signs shall be prohibited. If a building
fronts on two or more streets, a project sign may be displayed on
each frontage.