What is an Apron?

Definition of Apron in Construction
The decorative piece of trim located under the window sill on the interior of the structure. This could reference a piece of architectural trim at the bottom of the window on the exterior also, but normally referenced to interior trim. The term apron is also used in construction to identify any adjacent piece or component that is under another primary element or in the case of highway work, alongside the primary roadway or travel lane. Apron is terminology that is applied to several different construction elements, depending upon the trade and the region of the country. However, normally it references an adjacent item or trim that would create an apron to the primary piece.