Model building as a hobby involves the creation of models either from kits or from materials and components acquired by the builder. A scale model is most generally a physical representation of an object, which maintains accurate relationships between all important aspects of the model, although absolute values of the original properties need not be preserved. This enables it to demonstrate some behavior or property of the original object without examining the original object itself.
The most familiar scale models represent the physical appearance of an object in miniature, but there are many other kinds. Building models are scale models of structures. They are commonly used in model railroading as well as wargaming and diorama making. Architectural models are also made to demonstrate and promote buildings before they are constructed. Many building models do not come from kits, but are handmade. Small scraps of random items found around the house often come in handy when creating many models. Color labels from magazine advertisements are often used as signage for modeled stores, for example.
Some model makers commonly make copies of model-building items by constructing a simple mold from clay, inserting the item within the mold, then pouring plaster into the mold. Other modelers use whatever materials will give the best and most realistic look. For instance, a metal structure would be made of metal, a wooden structure wood. Special attention is taken to make sure that all elements are in the correct scale; even the grain of the wood used must be fine enough to look in scale.