Plywood is the usual type of composite wood panel that is used. Marine-quality ply is durable, less prone to warping than ordinary plywood, and does not shrink or split. It can be used as a base for laminate application (see below). Marine ply is often made from tropical hardwood, which might be an unsustainable source and therefore unacceptable under certain circumstances.
This is long lasting when undamaged, and can be produced to a very high standard. Good reproduction, a wide range of colours and fine detail are possible. This is an expensive medium, and when chipped it is difficult to repair properly. Stones or metal implements can easily chip it, and the steel base will rust quite quickly in the open air.
Glass-reinforced plastic (fibreglass)
This can be used to produce extremely durable panels in a variety of colours and finishes. It can be used as a base for printing or painting, or can be constructed with printed materials laminated into it (see below).
Transparent unbreakable materials like Perspex can be screen printed in reverse so that the message is visible through the material. High-quality printing is possible, but the surface of the Perspex is easily damaged by scratching or gouging.