The table 200 represents that only small dots should be formed in the range Cd1 of relatively small tone values. The locking unit is equipped with a coupling that has been arranged to allow the movement of the twistlock head in all directions on a plane perpendicular to the rotation axis of the twistlock head. The propellant urges the fluid from the fluid cavity through the passage upon initiation of the propellant. A seal member 8 is provided along an inner peripheral edge of a body panel PB defining a door opening S of the vehicle body, and a through opening 9 through which the arm member 3 is protrudable is formed in the seal member 3. The length of the cross brace may be changed via a straight slot in the first bar and at least one projection in the second bar extending into the slot, to allow the bars to slide in and out over each other.