Jack: in practical mechanics, portable hand-operateddevice for raising heavy weights through short distances, exerting great pressures, or holding assembled work firmly in position.
This shutter device for fading a picture can be operated by hand.
这个使画面惭入的遮板装置可以用手操作。
3
Automatic feed is realized, the auxiliary device of the high-efficiency electric iron can be operated by one hand and the other hand can freely catch a device to be soldered.