The bedknife consists of a fairly thin piece of spring steel, attached by many small screws to a sizeable chunk of cast iron (the holder) which is in turn attached to the mower by its two end-pivots. The spring steel can only be sharpened while attached to its own holder, or it has no particular shape. The assembled bedknife is quite rigid, and can be ground flat by supporting the holder by its two end-pivots. The screws attaching the spring steel to the holder should never be loosened, tightened or adjusted by the owner: otherwise the spring steel will take on a different shape, and have to be ground again.