First, cut the scalp to expose the skull. First, drill four holes (about 1cm in diameter) at four points (four corners of the trapezoid) in the operating area (drilling through the whole skull). Then, under the protection of elastic steel sheet, put a linear saw blade into one eye and come out from the adjacent other eye, then saw the skull and saw the four eyes in turn, so that the trapezoidal bone plate can be taken out and the work before craniotomy can be completed.