A good many times in a day’s dry fly fishing you may need to throw a curve into your line after your line, leader and fly are on the water and have completed part of their drift. Suppose, for instance, that you made a straight cast—cross-stream—over some fast current into slower water beyond before you realized the speed of the intervening current.
Maybe, too, you threw an upstream curve cast, but the fast water drifted your line down so fast that you now have a down stream bulge in your line.
This is just about to cause a drag on your fly—and spoil your chances at a good fish in the “pocket” where your fly is floating. You need to fix or mend the curve of your line. You can do it this way:
Lower the tip of your rod close to the water, at the same time taking up any slack line with your left hand. Then, with your rod tip, make a partial side roll cast—up, ovej and down in an up-stream direction. This cast must be done with just enough power to pick up the curved line only and* to turn the downstream curve of your line over into a corresponding up stream curve. Be careful not to use too much power or you will cause a drag yourself. Such a fly casting technique will usually give a feeding fish the chance to take your fly before it drags.