- This article is about a general descriptor. If you are interested in other uses of the term such as rolling stock consider going to the Trains glossary.
Stock is an adjective used in the sense of a standard or factory-original item (ie: the original meaning of stock car racing or an item stocked by a retailer.)
A stock model is the model pictured on the box of a LEGO set for which instructions are supplied. A stock model requires only that the builder be able to follow directions and therefore is in contrast to MOC. For this reason some AFOLs deride those who only build stock models as being "less creative". However, it is rare to find a LEGO enthusiast without at least one stock model still assembled on a shelf somewhere.
A stock element is one that has not been modified from its factory specifications. Purists prefer to use only stock elements and appreciate the challenge inherent in a limited pallette while customizers enjoy the challenge of cutting, painting or otherwise modifying parts to fulfill their vision.