When we cook things to the boil and would like to continue cooking,in order to prevent liquid spilling out of the wok(pot).We would usually find something to put across the rim of the wok under the lid or make the lid on a slightly overhung position,(so that the steam can be let out and the liquid would not spill 这是我替你加上去的:(这样做)便可以把蒸汽放出,液体就不会溢出锅外)
And the design of this product is that you only need to lift up the lid and give it a slight twist,the stick up part of the lid will hang on the rim of the wok and an opening would appear so that the problem of spilling will be solved.