To effectively and easily seal a jointed part between ridge cap fasteners assembled with each roof board in particular, in the case of forming a roof part via a plurality of roof boards jointed to each other.

For a jointed part at the end of each ridge cap fastener 30 of roof boards 01 adjacent to each other, a bonding seal means 31 having approximately the same cross section as the fastener 30 is used and coupled to the fastener 30 from the upper rear side thereof, so that both sides of the bonding seal means 31 cover each cap fastener 30 of the roof boards 01 jointed to each other. The jointed part of the fastener 30 is thereby concealed.