In this step, you are going to take your triangular needle file and remove the material from beneath the peaks.
This step removes some of the the weak points in the picks, helping to ensure that they don't snap off inside locks.
In the first picture, I am pointing to the area you need to remove with the tip of my file. As the pictures progress, you can see the material going away. I didn't want to take too many intermediate pictures because I didn't want to get metal powder in my camera. Continue to follow along with the pictures as I have them laid out. You are getting so close now.