To perform repair and exchange by removing only the side wherein maintenance is effected by a method wherein an operation part and a passive part are separately arranged outside and inside a rail and the two members are engaged together for coupling.

A rotary body 3 is rotated togetherwith a handle 2 and by drawing a circular locus centering around a lock shaft in a state that an engaging member 4 is engaged with an interlocking member 5, the interlocking member 5 is reciprocated longitudinally of a rail along a pedestal 1. An operation part 10 to rotate the rotary body 3 in the empty chamber of the pedestal 1 is formed such that the rotary body 3 and the interlocking member 5 are smoothly moved. A hinge is rotatably held at the central part of a case 21 of a passive part 20 and tooth parts engaged with a pinion are formed facing each other on two racks. A fixing part for linkages m1 and m2 continued to an airtight device at an end part in a longitudinal direction is arranged, A coupling port engaged with and disengaged from an interlocking member 5 is formed at least one of the two racks and through rotation of the pinon, movement in an opposite direction from the release port of the case 21 is practicable.