A mowing device including a disc, the disc providing a mount for at least one knife, said knife being pivotably mounted to said disc by a pivot pin, said pivot pin defining a mounting axis, such that the knife can rotate about said pivot pin between a first extended position and any retracted position, said disc being constructed of a basic material thickness and comprising a mounting surface; said mowing device including a knife adapter comprising a cylindrical aperture and a projection; said pivot pin comprising a first cylindrical section of a first diameter to fit into said cylindrical aperture in said knife adapter, and a second cylindrical section, of a second diameter, with a groove defined by a groove width and a pin section thickness at the groove of a dimension less than said second diameter; said mowing device including a retainer constructed of a material thickness equal to or less than the width of said groove, with a key-hole shaped aperture defined by a first circular section with a first inside diameter larger than said second diameter of said pin and a slot shaped section with a width that is greater than said pin section thickness but less than said second diameter of said pivot pin; wherein said slot-shaped section of the retainer engages said groove of said pivot pin to retain said pivot pin while said projection of said knife adapter engages said retainer.