PURPOSE: To facilitate execution of work by fixedly clamping the sides of a setting bed material with a fixing piece on both sides of a joiner and installing a wood trimming surface of panel to a side wall of a rising piece of the joiner by way of a gasket member.

CONSTITUTION: A column-shaped setting bed material α constructed to meet the mounting pitch of a panel B is installed and clamped between fixing pieces 2 and 3 of a joiner A and fixed with a side α1 of the setting bed material αwith a fixture β. A wood trimming face B1 of a building panel B is placed into cross contact with the side wall of a rising piece 4 of the joiner A by way of a gasket member 5, thereby forming a joint section. It is, therefore, possible to form the joint section from the rear side of a building.