Patent ID: 7712279

Claim:
A knock-down roof curb for supporting an appliance on a sloping roof, said roof curb comprising a plurality of metal wall members connected to form a rectangular frame having four corners which can be placed on the roof, a plurality of extension boards for extending the height of the curb, each of said wall members having an outside surface and a channel extending in from an inside surface and running along an upper edge of each of said wall members, said channel being inwardly disposed so that said outer surface remains flush with an outside surface of a particular extension board above it, said channel receiving a lower edge of each of said plurality of said extension boards and support said lower edge of each board from below while laterally containing each lower edge between two substantially vertical channel walls, the extension boards having top edges for receiving and supporting an appliance thereon, a plurality of connection blocks including bores which receive fasteners through an adjacent pair of wall member ends at each of said corners, so as to connect said frame; an opposed pair of said extension boards included in said plurality, said opposed pair being taper cut to compensate for roof slope so that said top edges provide a level surface for supporting said appliance.