To prevent adhesion of refuse or the like, lighten an impact at the time of falling-in and tightly set a door by urging the inside of a receiving frame body with springs in which a pair of rocking bodies are shaft-supported and are inserted in pivots so as to near the projection parts of the rocking bodies at the normal time and to grab a falling rod at the time of engagement.

Pivots 3, 3 are provided in a hollow box-shaped frame body 1 substantially at right angles to the direction of opening and closing of a door, and rocking bodies 4, 4 rotating around an axis line are symmetrically pivoted on the center line of a falling rod 10. Torsion springs 5, 5 are inserted in the pivots 3, 3, and hung and spanned on spring hanging grooves 41, 41 and 13, 13 provided in the neighborhood of the center of the rocking bodies 4, 4 and the inner bottom part of the frame body 1. At the normal time, projection parts 42, 42 of the rocking bodies 4, 4 are urged to be neared. When the door is closed and the falling rod 10 is engaged in the frame body 1, the edge of the falling rod 10 caused the projection parts 42, 42 of the rocking bodies 4, 4 to rock against the springs 5, 5. The falling rod 10 is grabbed by the projection parts 42, 42 of the rocking bodies 4, 4, and the door is restrained without any looseness.