If your pastel drawings are on beautiful paper like Arches, Rives,
Pescia, etc., which have watermarks and a deckle edge, consider
cutting the matt window so that it is 1/4" larger (each side) than the
size of the paper, to show off these qualities of the paper. Use an
archival board for the window and the backing. There is a self-
adhesive linen tape that can be used to adhere the art work to the
backing board. Let me know if you need further instructions.