<P> Exterior signs were a prominent feature of the streets of London from the 16th century . Large overhanging signs became a danger and a nuisance in the narrow ways as the city streets became more congested with vehicular traffic . Over time, authorities were forced to regulate the size and placement of exterior signage . In 1669, a French royal order prohibited the excessive size of sign boards and their projection too far over the streets . In Paris in 1761, and in London, about 1762 - 1773, laws were introduced which gradually compelled sign boards to be removed or fixed flat against the wall . </P> <P> For the most part, signs only survived in connection with inns, for which some of the greatest artists of the time painted sign boards, usually representing the name of the inn . With the gradual abolition of sign boards, the numbering of houses began to be introduced in the early 18th century in London . It had been attempted in Paris as early as 1512, and had become almost universal by the close of the 18th century, though not enforced until 1805 . Another important factor was that during the Middle Ages a large percentage of the population was illiterate and so pictures were more useful as a means of identifying a public house . For this reason there was often no reason to write the establishment's name on the sign and inns opened without a formal written name--the name being derived later from the illustration on the public house's sign . In this sense, a pub sign can be thought of as an early example of visual branding . </P> <P> During the 19th century, some artists specialized in the painting of signboards, such as the Austro - Hungarian artist Demeter Laccataris . Pending this development, houses which carried on trade at night (e.g. coffee houses, brothels, etc .) had various specific arrangements of lights, and these still survive to some extent, as in the case of doctors' surgeries, and chemists' dispensaries . </P> <P> Several developments in the early 20th century provided the impetus for widespread commercial adoption of exterior signage . The first, spectaculars, erected in Manhattan in 1892, became commonplace in the first decade of the 20th century and by 1913, "the skies were awash with a blaze of illuminated, animated signs ." In the 1920s, the newly developed neon sign was introduced to the United States . Its flexibility and visibility led to widespread commercial adoption and by the 1930s, neon signs were a standard feature of modern building around the world . Privilege signs, which employed the manufacturer's brand as a form of retail endorsement, were common on retail stores during the 20th century, but their use has waned as retailers gained increasing power in the late 20th century . A small number of privilege signs are still present, but most have become abandoned ghost signs . </P>

What are the two main parts of forming signs