PURPOSE: To facilitate the insertion or withdrawal of an object to be cooled by a method wherein a part holder is pulled up to make a fixed rod abut on the lower end of a slot and rotated to move a bit downward until the other holding plate abuts the fixed rod so that both the holding plates are opened in a sector centered on a pivoted part mutually while being kept in this condition with a hook.

CONSTITUTION: A fixed rod 11 parallel with a liquid surface is arranged and a slot 14 so inclined with an interval from a groove bottom part reducing upward is arranged on both sides thereof having a groove-shaped cross section. A holding plate 13 is provided with the fixed rod 11 fitted into the slot 14. A holding plate 15 is so arranged as to have a groove-shaped cross section and be inserted internally into the holding plate 13 with the groove-shaped cross sections thereof facing each other on the side of releasing while mounted between the holding plate 13 and the fixed rod 11 to be pivoted into a pivot support hole 17 of one holding plate 13. Moreover, a hook 18 is fixed on the external surface of a groove bottom part of the holding plate 15 in such a manner as to allow the receiving of the fixed rod 11 from below with the fixed rod 11 abutting on the lower end of the slot 14. The holding plates 13 and 15 are lifted to form an opening, through which indeterminate shape articles are inserted or taken out.