Kitbashing involves combining or modifying parts from one or more kits to make a custom model. The term has been extended to apply to models and toys such as Transformers that are not sold as kits. Kitbashing is sometimes called customizing. The purpose of a kitbash is to obtain something that can't be bought, to improve something that can, or simply to engage in a refreshing exercise of creativity. Kitbashing is also frequently used in the toy industry by designers to develop "proof of concept" models to showcase an idea.