If you are casting in a spot where you have high trees behind you and overhanging branches above your head you’ll have to use a special fly casting technique, called side roll cast—sometimes called the switch cast. This is done, after the slack line has been taken in by the left hand, by lowering the point of your rod towards the fly and then bringing the rod backward horizontally and slightly upward in a smooth, slightly accelerating motion until the rod is just a little more than the usual 22 1/2 degrees beyond a straight sidewise direction.
This backward movement is then smoothly converted into an upward circling action of the rod tip that blends into a powerful accelerating side cast in the direction you want your fly to light.
The forward cast technique is made with the muscles of the forearm and finished with a sharp thumb pressure. The wrist should be kept stiff.
The hand, with the right hand side roll, is carried palm up. The side roll cast can be made either from the right or left hand side.
In the left hand side roll, the palm of the hand is turned down.
If you are using the wrist-action grip, you substitute wrist action for the thumb pressure and most of the forearm movement; but keep the rod angles the same.