PURPOSE: To not only easily set a tiltfoot at a housing position but to hold a set position even when a force in a lateral direction is applied to the tiltfoot set at the set position and to dispense with components such as a spring, etc.

CONSTITUTION: When the tiltfoot 20 is set at a set position side, and weight is applied to the tiltfoot 20, the rotary shafts 27, 28 of the tiltfoot 20 are slided in guide holes 17, 18 by applied weight, and the clicking part 29 of the tiltfoot 20 is abutted with a stopper protrusive part 16, which supports the applied weight stably. When the tiltfoot 20 supports the applied weight, motion to return the tiltfoot 20 to the housing position even by the application of an external force can be blocked by the clicking part 29 and the stopper protrusive part 16.