LEGO Master Builder
LEGO Master Builders are people employed by the LEGO company to build models. According to members of the Enfield Model Shop, there are various types of Master Builders that have been at LEGO, performing various tasks.
Master Designers are occasionally referenced as "Master Builders", and are generally responsible for designing and building promotional displays for LEGO. These may include models for LEGO-themed events, trade shows, retail stores, or other venues. Some tasks performed by other "Master Builders" include copying models that were designed by Master Designers. Often times, this happens when a model is to be sent out to many retail stores, and many copies are required.
Master Builders also refers to builders at Legoland theme parks. These builders are responsible for maintaining existing models, creating new displays, as well as interacting with visitors to the parks (talking with guests, judging building competitions, organizing build events, etc).
Master Builder Searches
LEGO has had several "open" competitions for new Master Builders at Legoland parks. In 2003, the process was widely publicized for finding one new Master Builder to add to their 6-person team in Carlsbad. The group hiring model builders toured 8 cities in the USA (Carlsbad CA, Washington D.C., Boston MA, Charlotte NC, Las Vegas NV, Phoenix AZ, Los Angeles CA, and Santa Ana CA).
Applicants each started with an initial interview session, with well qualified interviewees proceeding to the "second round"-- a building challenge to construct a model from 2,000 LEGO parts in 45 minutes. After this challenge, finalists from each city were invited to Legoland, CA for the third round of building, where the lucky Master Builder was to be selected. In the end, three contestants were chosen as Master Builders, rather than just one.
Subsequent Master Builder searches have been conducted, although do not seem to have been as publicized as the US event in 2003, which received much attention from LEGO fans as well as the general media.