How to Use a Mason's Line. A mason's line is one of the most important tools of the trade. Also called mason's twine, the line keeps the block straight on the wall allowing for greater accuracy and faster laying. It's a great time saver because you don't have to stop work to pick up your level as frequently. Here's how to use a mason's line to get a nice, straight wall.
Things You'll Need
Braided Mason's Line
Brace and level a 2-by-4 inch corner pole.
Slip the braided mason's line inside the groove of the line block.
Wrap it around the notch on the line block twice, and slide it into the groove again.
Face the hook of the line block toward the rear corner of the cement block, and hook the line block over the outside of the block.
Run your line to the next corner. The line should be taut and close to the block you are laying, but you should have enough room to wipe off the extra mortar without bumping the line.
Lay your block so that the top of the block matches up with the line you've established. Follow the line as you are laying, and slide the line blocks up as you build up the wall.
Check your wall periodically with a level to make sure your work is plumb and level.
Look for nylon braided mason's twine at a builder's supply or home improvement store. While it costs slightly more, masons prefer braided twine to wrapped twine, which can stretch. Purchase several line blocks, small wooden tools to hold the mason's line as you are laying. You may also need a metal line trig to keep the line from sagging if the wall you're building is longer than 50 feet.