Raised-face seat. A groove around the seat collects particles pushed aside by the knife and prevents clogging. When the valve opens, media pressure cleans the groove.
The secret of successfully pressed hems is to use very little pressure so that the edge is not flattened to produce a knife edge.
成功熨烫底边的窍门是用很小的压力，这样就不会倒伏而产生一条刃形边缘。
3
By applying this principal to the knife you can see that with a keener edge there's a greater concentration of the pressure on the edge, so it takes much less force to make the knife cut.