The pinch wrap may be the most important basic fly tying skill there is.
To begin, get your tying thread positioned at the precise location where you want a material tied in. Collect and prepare the material. Oftentimes this will require keeping the tips aligned. With the material held in your right hand, measure against the hook or hook shank to get the correct length then transfer that measurement to directly over your tying thread.
Pinch the material on top of the hook shank between the thumb and index finger of your left hand. Raise your tying thread to vertical and sneak it between the pad of your thumb and the material, and give a little squeeze. Bring your thread over top of the material then back down the far side of it, beneath your index finger. Pull down to close the thread loop then once again bring your tying thread up to vertical. Give another little pinch with your fingertips and pull straight up on your tying thread with a fair bit of tension. The material should now be well secured to the top of the hook shank right where it’s supposed to be.
The idea of the pinch wrap is to keep material anchored to the top of the hook shank rather than spread around it.