a mould is basically a blank which fibre glass or other more exotic medium can be laid up in to form the shape of the desired design. The attached photos are of a mould for a 45′ motor yacht.

For an in depth explanation of moulds and their uses click on the link below.

http://www.boats.com/reviews/fiberglass-boatbuilding-you-start-with-a-mold/#.WUsYXuuGNhE