PURPOSE: To reduce the quantity of excavated or back filling earth in a laying place by inserting the vertical part of a male tower-type projection into a female pinching member assembled in a U-shaped wrapping member for joinedly connecting a concrete structure.

CONSTITUTION: First a pinching plate 3 to be plate-shaped is integrated on the back of a cylindrical section 2 in a U-shaped wrapping member 1, and a spring 5 is wound on a main shaft 4 to form a female section structure. The pinching plate 3 is pushed to open the cylindrical section 2, and a protrusive vertical part 8 of a tower-type projection 7 integrated by burying a horizontal part 6 in a male body is pinched for forming a joinable structure. In this case, both the ends of the main shafts 4 are assembled in the recess 9 of the U-shaped wrapping member 1 to integrate them, and a tightly connecting reinforcement 10 to tightly connect the wrapping member to the reinforcement is attached for integrating the female section with the main body. Next, the tower-shaped projection 7 of the male section may select either a buried type in a structure body or a detachable type threadedly attached to an inserted body.