This device clamps firmly to the bottom plate of a reel mower and sharpens the blades as they turn. Made from extruded aluminum, it is 20" long, but can be trimmed to fit mowers as narrow as 10". It automatically sharpens the blades to the correct angle.
By keeping a good edge on your blades, you not only make mowing easier, you minimize tip browning by ensuring that the blades shear the grass rather than tear it.
It uses replaceable abrasive strips; three come with the sharpener. Replacement strips are available.