I think by genoa railing he means a genoa "track"... it's a long T track, mounted on the toe rail that can accommodate a large range of sail sizes and additional equipment for other purposes. The toe rail location creates the wide sheeting angle often preferred for reaching. On my genoa track I have mounted lead and turning blocks for spinnakers and all upwind sails, an adjustable EZ glide jib lead system, a track mounted mid ships cleat, a slider for the spinnaker twing controller... and something else I can't think of at the moment. Oh, did I forget to say a genoa track is pretty darn handy.