Over the past weekend, I got some tin up on the roof of the pole shed. I installed blocking between the purlins and that helped tremendously. I might be doing this the newbie way, but I'm using a straight edge to draw a line horizontally from the screw on the preceeding panel to the center of the purlin, then using a punch and a hammer to punch a hole where I want a screw to go. Finally shooting a screw in the hole. I learned a while ago on our other metal building that screws often dance around and don't start where you want them to start.... so best to either punch a hole or at least make a dimple for the screw to start.

Another detail... I'm damn near 60 and running up and down a roof like a spider monkey isn't as fun as it used to be.