PURPOSE: To enable free variation of the inclining angle of a table, by providing a positioning pin being inserted through a pin hole associated with an endboard and a pin hole associated with a vertical wall section and a mechanism for clamping the endboard to the vertical wall section.

CONSTITUTION: A plurality of pin holes 6 for positioning a table 3 with a desired inclination angle are formed with desired intervals through the face of the endboard 4 facing against a vertical wall section 2. Two pin holes 5 matching with the pin holes 6 in respective rows formed in the endboard 4 are formed at the shoulder section of the vertical wall section 2. Furthermore, first clamp mechanism C1 for clamping the endboard 4 to the vertical wall section 2 and second clamp mechanism C2 for clamping the intermediate section of the table 3 to the base 1 are provided as an anti-vibration device for the table 3.