PURPOSE: To facilitate mounting work by providing a fastener having an inclined piece having the same slope as that of an inclined beam on the upper part between the inclined beam and a horizontal muntin of an external wall panel to connect them to each other.

CONSTITUTION: A fastener 3 as a hardware having an inclined piece on the upper part thereof with an L-shaped section is formed, and the upper inclined piece of the fastener 3 is contacted with the lower end of an inclined beam 2 and is connected with a bolt. After that, the lower part of the fastener 3 is connected to an external wall panel 1 consisting of a plurality of muntins 1a and a horizontal muntin 1b with a bolt. Accordingly, the external wall panel can be easily mounted even to the inclined beam.