Bringing home a kit, opening it and assembling the pieces is how many people view model building. This is a fine hobby for those who enjoy creating something from parts, but it is nothing like the job done by professional model builders. They are provided with a set of plans just like the home hobbyist, but they must then build their models completely from scratch. There are no instructions, pre-fabricated pieces or a set of paints included.
Professional craftsmen in this area work in many different shops and professions, and they build the items dreamed up by designers. Their goal is to create a lifelike representation of the design so it can be improved if necessary or passed on to the manufacturing section of a company if the design works. They generally have large shops where they create the models, and some of them are full sized while others are scaled down.