PURPOSE: To make it possible to efficiently load by providing a double reinforcement spacer to set an interval between an inner and outer cages of the double reinforcement incorporated into a Hume pipe and a tool to mount the spacer to the double reinforcement.

CONSTITUTION: A temporary tool stop section 18 of a double reinforcement spacer 10 is inserted and fixed into a temporary spacer stop section 35 of a spacer mounting tool 30. After that, the tool 30 is inserted through between an outer cage screw reinforcement 54b and inner cage screw reinforcement 52b. Then, a reinforcement pushing section 37 is pushed against the upper part of an outer cage vertical reinforcement 54a, and the force fit of the outer cage vertical reinforcement 54a into a reinforcement holding section 16 is made with the force of its grisp. After the force-fit thereof, a holding port of the tool 30 is opened to remove the spacer 10 from the temporary spacer stop section 35, and it is mounted to an inner edge vertical reinforcement 52a and outer cage reinforcement 54a. According to the constitution, an interval between the inner and outer cages can be kept equal.