You are standing in mid-river using a 9 foot rod and you decide you would like to switch from a floating fly line to a sinking tip fly line. You can easily remove the reel spool with the floating line from the reel and insert the reel spool with the sinking tip line. Now pull fifteen feet of line with the leader attached from the reel. Take the fly rod apart at the ferrule in the middle of the rod and place the tip section of the rod under your arm. Thread the leader and line through both sections of the rod then put the tip section back on the butt section at the ferrule and you are ready to fish. This works fine with two piece and four piece rods.