| 摘要 |
There are provided an operating knob 42 capable of movement operation in a front-back direction with respect to a right and left side support part 31, a rod member 45 whose front end is joined to the operating knob 42, a back edge stopper 47 which is moved in the front-back direction through the rod member 45 and also is abutted on the back edge of the mask 15 by fixing operation of the rod member 45 by the operating knob 42, and a front edge stopper 53 abutted on the front edge of the mask 15. |
