Because the jambs are routed with rounded or "radiused" edges along their lengths to Michael's specs, the joints where the head and side jambs meet must be mitered rather than built with the conventional rabbet joint. The relatively narrow casing or trim is also radiused. The casing must be fastened back of the radius on the flat part of the jamb edges and the stainless finish nails and brads which fasten them to the jamb must be fired carefully back of the other radius on the casing to avoid "blowouts" (protruding nails). Such errors cannot be easily fixed or hidden in the naturally finished casings.