To provide an auxiliary tool for mounting a verge tile which prevents formation of a gap between the verge tile arranged on a verge of a roof and a vergeboard.

The auxiliary tool is formed of an almost rectangular plate body (11), a first block portion (15) which is shaped so as to be fit for blocking the gap (5) between the verge tile (1) and the vergeboard (3) and extends from one side-edge (13) of the plate body (11) in a direction almost at right angles to the plate body, and a second block portion (19) which is shaped so as to be symmetrically the same as the first block portion and extends from the other side-edge (17) of the plate body in a direction almost at right angles to the plate body and opposite to the first block portion. Then, one of the first and second block portions is nailed to either a tile support body (21) or an upper surface of the vergeboard, and the other block portion functions to block the gap between the verge tile and the vergeboard. By turning the plate body upside down, the auxiliary tool is available for either of the mutually opposed verges (23a), (23b) of the roof.