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The fastest way to rabbet the back of a cabinet is to do it all at once, after the cabinet is assembled. Unlike rabbeting individual pieces before assembly, I don’t have to worry about where to start or stop a rabbet or whether each rabbet will be level with its neighbor. As long as the sides of the cabinet are level, the rabbets will be level, too.
I use a rabbeting bit with a bearing to make the cut in one pass. To balance the router, I cut a milled 2×4 to fit tight into the opening and position it level with the side. Then I clamp across the cabinet to keep the board from shifting. I rout the long sides first, then cut the 2×4 to fit the short sides. The bit leaves round corners, of course, so I just round the corners of the back to fit. –Tom Caspar
