Abstract: A reel mower assembly which includes a mower reel mounted to a frame, a drive operative to rotate the reel about a reel axis, a magnetic backing plate mounted to the frame and a magnetic bed bar retained in proximity to the backing plate in an operating position. The assembly includes a bed knife interposed between the backing plate and the bed bar, with the backing plate providing additional magnetic attraction between the bed bar and bed knife. The assembly includes an engagement device for preventing sliding movement of the bed knife with respect to the bed bar while allowing the bed knife to move away from the bed bar and backing plate when a separating force is exerted on the bed knife in a direction away from the bed bar that is greater than an attractive force exerted on the bed knife by the bed bar.