Go to another layer so you have a good view and then make sure you have the crosshair in origo. Go to front view and add a new cube. Select the two bottom right vertices and delete the edge between them.
Still in front view select the left side vertices and move them a bit to the right.
Go to top view. Press ',' to change the pivot point to bounding box center. Select the right side vertices. Press 'S' then 'Y' to scale in y-axle. Scale them up abit.
Use the knife tool and cut the box in half.
Select the middle vertex that is created to the right. Go to side view and move it up.
Go to top view and zoom out. Move the 8 (I think) units to the right (remember the CTRL key).
Goto the edit panel and set the screw/spin/dup panel to these values. Press "Spin Dup".
Select all vertices. Remove doubles, then remove all but the three rightmost boxes. You now should have something like this.
In front view move the cursor one gridunit up and snap it to grid (SHIFT-S).
Fill the gap between the three boxes like so. Remember to make quads.
Select the top of all three boxes. Go to top view and then press '.'. Now scale them so they line up like on pic below.
Select all vertices again and spin dup with the same settings as before. Deselect and reselect all vertices and remove doubles.
In front view use the box tool to select all the top vertices. Extrude two times so that you get something like the pic. Remember to use 'Z' to constrain the movement to the z axle.
Move the cursor to origo again then select the bottom edge and move it one unit up (CTRL-key helps here).
Deselect the bottom vertices and select all but them. Move the selected ones straight up.
Select all vertices. Press SHIFT-D then right click ONCE. Press 'M' and select "global Z".
Remove the doubles then TAB out. Set the edit menu to level 2 subsurf and hit smooth. Any black thingies can be removed with the "Recalc normals" trick. And the result...
