PURPOSE: To permit a fingertip operation by providing the rear surface of an iron base plate with bearings for adjusting turning and bearings for adjusting sliding, fitting the horizontal shaft parts of legs having an approximately U shape into these bearings for adjusting sliding from the side of the bearings for adjusting turning, energizing the front ends thereof backward by means of springs and holding the front ends to turning positions by means for detaining the bearings for adjusting turning at the time of turning the legs.

CONSTITUTION: Detaining pins 20, 21 move in guide holes 12, 13 of detaining adjusting holes 18, 19 formed on the peripheral walls of the respective bearings 4, 5 for adjusting turning and engage with engaging holes 14, 15 or 16, 17 when the horizontal leg parts 63, 73 of the supporting legs 6, 7 are turned around the horizontal shaft parts 62, 72. At this time, the front ends of the horizontal parts 62, 72 are held pressed and energized backward, i.e., to the side of the bearings 4, 5 for adjusting turning by the coil springs 10, 11 and, therefore, the detaining pins 20, 21 are automatically engaged with the detaining holes 14, 15 or 16, 17. The supporting legs 6, 7 are held in an open state when the pins 20, 21 are detained to the detaining holes 14, 15. The legs are held in a folded state when the pins are detained in the engaging holes 16, 17.