This step has you drill the bottom wing box J-stiffeners to the bottom flange of the main spar except in the areas where nutplates will go, and then you "roll them 180 degrees and re-cleco them onto the upper spar flange" so you can drill the holes in those areas you skipped.
Which way do you "roll them" 180 degrees? There are 4 possible orientations at the end, of which 2 seem potentially sensible when reading the plans that say to "roll" the stiffeners:
Roll about the plane's roll/longitudinal axis: this puts the short stiffener (which belongs inboard) outboard and the long one inboard with the J-stiffener flange pointing "in" toward the spar web
Roll about plane's pitch/lateral axis: this puts the short stiffener inboard where it belongs, with the J-stiffener flange pointing "out" away from the spar web
Which way do you "roll them" 180 degrees? There are 4 possible orientations at the end, of which 2 seem potentially sensible when reading the plans that say to "roll" the stiffeners:
Roll about the plane's roll/longitudinal axis: this puts the short stiffener (which belongs inboard) outboard and the long one inboard with the J-stiffener flange pointing "in" toward the spar web
Roll about plane's pitch/lateral axis: this puts the short stiffener inboard where it belongs, with the J-stiffener flange pointing "out" away from the spar web