I went to a home show, and they were giving these away. It's a piece of wood, L shaped, grooves in it. It is used to hold the line on the outside corner of blocks at a corner to use a guide for the next course.
I have googled about every combination of blocklayer, string, blocklayer's tools, blocklayer's hand tools, anchor, etc, etc, that I can think of, and can't find one that shows me how to wind the string on there.
Help out an old fart here. I know it's gotta be so very simple, but right now, it's got me baffled.
Steve