To obtain a jig by which a packing between a flange and an orifice can be replaced easily by a configuration wherein a receiver part which is fixed to a flange on one side is attached to the end of a screw rod and a movement part which presses a flange on the other side is screwed to the screw rod.

In a movement part 7 which is screwed to a screw rod 6, its protruding finger 11 is fitted to a flange 2a, and it is moved along the screw rod 6 without being interlocked with the rotation of the screw rod 5. A receiver part 8 is attached to the side of a flange 2b, and a tube body 15 is formed. A screw is not formed on the inner circumference of the tube body 15, and the screw rod 6 which is merely inserted can be turned freely. On the other hand, since the movement part 7 is screwed to the screw rod 6, it is moved together with the rotation of the screw rod 6. When the finger 11 is fitted into a screw hole 12, it pushes the flange 2a, and it expands a distance up to the other opposite flange 2b. Thereby, a gap is generated between a tube orifice and the respective flanges 2a, 2b, and a packing which is interposed between them can be replaced easily.