The Screw,tap.5x12 is the lowest priced item on this Heater Duct schematic.
On this parts fiche the Bolt-wash.,6x16 is the most specified component.
Parts such as the Heater Duct: Duct, R. Rr. Outlet, Duct In Assy Dr, Duct, L. Rr. Outlet, Duct, Rr. Heater are included in the Civic Wagon 1987 (h) Wgn Wv (ka,kl) Heater Duct parts fiche.