Using an electric planer right up to the edge or on rabbets often produces unsatisfactory results, as the machine leaves a lip that has to be removed by hand-unless you have the Festool HL 850 planer. The HL 850 lets you cut flush to an adjacent surface because it can plane across the entire width of the rabbet. Because the planer head is mounted to one side, it sits flush with the opposite side of the planer housing. The retractable side guard makes planing safer, and it swings up and to the side as the rabbet depth increases. Planing up to the edge in deep rabbets is no longer a problem.