An interface fitting for supporting a component of a structure to be assembled on an assembly jig, includes a component-side part, adapted to be attached to the component, and a jig-side part, configured to bear in an orientable way on the assembly jig. The support block further includes, a spacer member interposed between the component-side part and the jig-side part, which can be operated to adjust the distance between the component-side part and the jig-side part.