Mending the line
Mending the line is simply adjusting your fly line with the current so your get a natural drift with your fly. It is used with almost every cast in order to assist with the natural presentation of your fly or indicator. You will mend with dry flies, indicators, strippers (woolies) or hopper droppers.
Do not mend too often. One to three times is usually required on a long drift. I have seen guys mend so much that they really limit the cast’s potential because they are constantly moving the fly. The main trick to a good mend is making sure you LIFT THE LINE off the water before you adjust the line flow. Ideally you do not move the fly when you mend. Moving the fly does happen but over time you can perfect your mend to limit the movement. You will need to determine if you mend upstream or downstream depending on the stream’s flow. Here is a video to show you what to do: https://www.youtube.com/watch?v=9jUVN8W7U1c