The Line Bone is a tool that helps you set a level course for concrete block walls.
The Line Bone is simple to use (you will need 2 Line Bones):
First, tie the end of the string line to the knob on top of the Line Bone.
Next, place the Line Bone across the top of the first cinderblock at the middle divider as shown in the illustration. Run your line down to the end block.
Wrap the string around the body of the second Line Bone. Position the Line Bone along the top edge of the block at the center divider and wrap the string around the knob. Tighten the string if necessary so you have a taut, level line between your two end blocks.