It is suggested that various developments in technology and mathematics allowed the development of the professional ‘gentleman’ architect, separate from the hands-on craftsman. Paper was not used in Europe for drawing until the 15th century but became increasingly available after 1500. Pencils were used more often for drawing by 1600. The availability of both allowed pre-construction drawings to be made by professionals. Concurrently, the introduction of linear perspective and innovations such as the use of different projections to describe a three-dimensional building in two dimensions, together with an increased understanding of dimensional accuracy, helped building designers communicate their ideas. However, the development was gradual. Until the 18th-century, buildings continued to be designed and set out by craftsmen with the exception of high-status projects.
In most developed countries, only those qualified with an appropriate license, certification or registration with a relevant body (often governmental) may legally practice architecture. Such licensure usually requires a university degree, successful completion of exams, as well as a training period. Representation of oneself as an architect through the use of terms and titles is restricted to licensed individuals by law, although in general, derivatives such as architectural designer are often not legally protected.
To practice architecture implies the ability to practice independently of supervision. The term building design professional (or Design professional), by contrast, is a much broader term that includes professionals who practice independently under an alternate profession, such as engineering professionals, or those who assist in the practice of architecture under the supervision of a licensed architect such as intern architects. In many places, independent, non-licensed individuals may perform design services outside the professional restrictions, such design houses and other smaller structures.