The two nails method I use(d) means simply to hook the loose end of film through the perforations with one nail, unwind the roll to the other nail, hook another perforation, cut the film, secure the reel, put the cut film on to a cassette spool using a pre-positioned piece of sticky-tape (along the side of the workbench, for example) while leaving the other end of the cut film under control with the nail, reinforce it on the spool with another piece of tape, roll up the film on the spool, unhook the end from the nail and put it into the cassette, close the cassette, repeat. I was not referring to re-rolling bulk reels on to smaller ones.