Abstract: Disclosed is a channel shaped building panel especially adapted for installation on the underside of a roofing framework. The panel has opposed upstanding webs, one of which is provided with outwardly oriented generally L-shaped female locking and mounting means, and the other of which is provided with an inwardly oriented male locking means, both locking means terminating in detent ribs. At the juncture of the female locking means with its web, an integral inwardly oriented scabbard is formed, and a complementary outwardly oriented integral blade is formed at the juncture of the male locking member with its web. Upon upward insertion of the male locking member into the female locking member, the detent ribs interact in snap fashion, and the blade seats in the scabbard. The female locking and mounting member provides a surface for attachment of a fastener to the roofing framework.