Cover disks EN 576 are used on hand knobs EN 526.8 / EN 534.8 / EN 534.9 and handwheels EN 577.8 / EN 577.9 / EN 521.8, whether used together with a position indicator or without.
To mount these cover disks, simply snap them in position by hand. To remove them, pry them off with a flat screwdriver.