PURPOSE: To prevent an eaves gutter from being moved when a wind blows and, consequently, prevent the breakage of the eaves gutter and an eaves gutter coupling or elbow connected to the eaves gutter.

CONSTITUTION: An auxiliary jig 8 is an U-shaped sectional small piece, which has a window 81 opened to the side end on the upper surface and a window 82 on the side surface. The auxiliary jig 8 is inserted into the opening part of the C-shaped sectional outdoor side ear part 64 of an eaves gutter 6 and fixed thereto. The outdoor side ear holding part 4 of a gutter hanging tool 1 is inserted through the window 82 of the auxiliary jig 8 and engagingly locked by the outdoor side ear part 64 of the window 81 part. The indoor side ear part of the eaves gutter 6 is engagingly locked by the indoor side ear holding part of the gutter hanging tool. The eaves gutter 6 is mounted on the gutter hanging tool 1 in this way. When the outdoor side ear part 64 of the eaves gutter 6 is engagingly locked by the outdoor side ear holding part 4 of the gutter hanging tool 1, it is fixed by the auxiliary jig 8 so that it is never moved.