Before any conservation work is carried out, a rubbing is made of every panel. This creates an impression of the panel which is used to place individual pieces upon in their correct place when the panel is dismantled from its lead. The rubbing also serves as a record of the appearance of the panel before conservation. A rubbing is created by placing a piece of thin paper over the panel and gently rubbing a crayon over the surface. This picks up the raised profiles of the lead and the shape emerges.