To cast a fly rod, the angler pulls several feet of line off the reel. The rod tip is moved back then in a fluid motion and accelerating, it is moved forward as the line is released. In fishing streams and rivers, trees and shrubs on the bank may prevent an overhead cast. Another type of cast is the 'roll cast'. Using the rod tip the fisherman forces the rod tip down to roll the line forward. Most fly lines are rated by a weight system. A 1wt (one weight) is very light while a 13wt is very heavy. It would be suitable for large salt water fish. Rods (and reels) are rated by the weight of the line they are designed for. Unfortunately there is no one size for all kinds of fish and fishing situations.