PURPOSE: To automatize the sewing of a reinforcing piece on a corner part by adhering the reinforcing piece in which adhesive film of hot metal type is formed on the corner part of a flag, a curtain, or a banner, etc., by heating and pressurization.

CONSTITUTION: The reinforcing piece 2 in which a canvas sheet 4 consisting of the adhesive film 3 of hot metal type is cut in triangular shape is adhered by heating on both surface and back plane of the corner part at a side to be fixed on the hoist pole of a national flag base 1 by a home iron. A hole 5 is pierced through the corner part where the reinforcing piece 2 is adhered by heating, and a ring 6 made of metal for reinforcement is fixed on the edge of the hole 5, and a string 7 to mount the national flag on the hoist pole, etc., is inserted and connected.