for opening closing a door at either side includes a casing 10 fixed to the upper edge or the lower edge of the door 2 and covered by a cover 11 the casing 10 has pin slots 13a and 13b positioned near the opposite ends of the casing 10 so that corresponding hinge pins 7a and 7b of the main body 1 may come in and out of the pin slots 13a and 13b the cover 11 has a knob slot 15 formed in the middle and elongated longitudinally the switching knob 9 moves along the knob slot 15 pin grippers 20a and 20b are arranged in the region of respective pin slots 13a and 13b the pin grippers 20a and 20b have pin receiving grooves 23a and 23b for accommodating and restraining hinge pins 7a and 7b in the pin slots 13a and 13b the pin grippers 20a and 20b can pivot about respective pivot pins 21a and 21b therefore a retaining state in which the hinge pins 7a and 7b are restrained in the pin slots 13a and 13b as shown in fig3 can be switched to a release state where the hinge pin 7b is separated and released from the pin slot 13b as shown in the left side of fig4 when the pin gripper 20b pivots the retaining state is maintained when the hinge pins 7a and 7b come into the pin slots 13a and 13b again as shown in fig3 fig6 shows the case where the right hand pin 7a is separated from the pin slot 13a the pin grippers 20a and.