PURPOSE: To enhance a working efficiency and a safety in working by a method wherein an upper rail body is held above a form by a strut by hanging so as to be freely raised and lowered and horizontally moved.

CONSTITUTION: After concrete liquid is charged, an upper rail body 20 held by hanging is moved to be disposed above a form 10 by swinging an arm 3. After the upper rail body 20 is positioned to an upper-end opening 19, a ball screw 5 is manually rotated by grasping a crank handle 21. By the operation of the crank handle 21, the upper rail body 20 is lowered and raised to be mounted on the upper-end opening 19 and separated therefrom. At the time of a removal, after the upper rail body 20 is separated from the form 10 upwards, the upper rail body 20 is moved to a position out of the way of removal by swinging the arm 3.