DIN 6923 hexagon nuts with flange ( hexagon nuts with serration) The definition of flange nut, we generally call the nut with hexagonal flange face as flange nut. Flange nuts are also widely used. Generally, many screws and bolts need to be matched with flange nuts. Moreover, if flange nut is used, the fastening is very good. There is a flange face that fits the screws and bolts very well. The tightening performance is much better than the hexagon nut.