PURPOSE: To freely and surely pass a shaft or the like by providing a cross arm which is rotated around the center where a magnet is embedded at the tip in a cross manner of both sides of a roller in the space between an upper plate and a lower plate through which the shaft as the obstacle passes between the upper plate and the lower plate.

CONSTITUTION: A shaft is brought into contact with a roller 5 on the first unit of a block mechanism, and moved downward while the roller 5 is rotated, and a movable connecting shaft which is interlocked with the roller 5 is also moved downward at the speed of approximately 2.5 times that of the roller 5. Then, the shaft is brought into contact with a cross arm 4 on the first unit, and the cross arm 4 is rotated by 45° and passes the mechanism of the first unit. The shaft simultaneously passes the roller 5 on the second unit and the cross arm 4 on the second unit, and is moved downward while the roller 5 is rotated, and the movable connecting shaft which is interlocked with the roller 5 is moved downward at the speed of approximately 2.5 times that of the roller 5, and the cross arm 4 is also rotated by about 45° and the shaft passes the mechanism on the second unit.