I understand that the ECO Sock pattern becomes TRICKY in Rows 34 through 41 as the top of the sock is gradually increased. The increases work in the tubular double knit technique but the sock is NOT YET tubular! (a brain bending feat is at hand) -- so, let's more appropriately call this a "Flatfold" technique.
During the heel rows the bottom of the sock is established. In Rows 34 through 41 a FLATFOLD is created at each end of the needle and seems to get REALLY COMPLICATED.
The fold at each end distinguishes the bottom sock stitches from the top sock stitches. Right side knit stitches begin to be called "back stitches" and wrong side purl stitches are suddenly named "front stitches" as the piece is worked back and forth knitting odd rows and purling even rows.
After Row (RND) 41 the foot rows will be worked in tubular double knit.