As an SU neophyte I'm trying to draw a wooden street lamp arm for re-manufacture. This 4" wide cedar arm is 50" long and 7" deep on the horizontal until it inflects upward toward the lamp end. at the horizontal inflection point 31" from the lamp end, the underside tapers up from a 7" depth to a 3" depth at the lamp end. The top of the post is horizontal with no tapering. I need to show a double rabbet inside the bottom of the arm as a wiring channel. One rabbet is 1 1/2" wide by 1/4" deep and other, within the first, is 1" wide by 1" deep. I tried to create the double rabbets by pushing rectangles into the body of the arm. I was able to create the 1-1/2" rabbet easily as well as the 1" rabbet on the horizontal section but I have had no end of trouble trying to draw the last 1" sloped rabbet because the rectangle tool wants to connect to the wrong surfaces. I guess this is because two planes intersect and go past each other slightly at the inflection point without making a geometric connection.