[mechanickeith]

Have seen them before but have never used one. I just mark the head of the bolt & turn it!! 1 flat is 60*, 1.5 flats is 90* etc etc. I mark one corner of the bolt & if I am going say, 120 degrees more, I mark the block/part 2 corners to the right & turn the bolt till the marks line up. I have painted stripes on the side of my sockets. I put the socket stripe on the mark on the bolt & turn till it lines up with the mark on the block, head what ever.