A mason's line acts as a guide for setting bricks in perfectly straight rows. It's made of two mason blocks with slots to hold a mason line.
Affix the blocks to either end of the row of bricks, with the line pulled tight. The top of each brick in the row should just touch the top of the line.
Safety Tip: When working with mortar, always wear gloves and a mask or respirator.
Use a spade trowel to apply a generous amount of mortar to each layer of brick. Score a line through the center of the pile of mortar to allow it to spread. "Butter" the brick with mortar, spreading mortar on the sides that will affix to the bricks beside them. Use the handle of the trowel to knock each brick into place and to release any air bubbles that may be in the mortar underneath.
Using the sharp end of the trowel, scrape off any excess mortar that spreads beyond the joint. Finish cleaning off any other debris with a brush. Holding a spade trowel at a 30-degree angle, carve small lines between the bricks and the mortar. The lines will help protect the wall from the effects of precipitation.
Most walls require smaller bricks at their ends. Before cutting a brick, place it in a bed of sand or dirt to absorb the shock of the blow. Place the sharp end of a brick chisel at the line where you want to cut. Use a hammer to tap the end of the chisel, scoring lines on all four sides where the brick must be cut.
After scoring the lines, hold the chisel on one of them, slightly angled toward the side of the brick that will be kept and used on the wall. With your other hand, strike the handle of the chisel with a hammer. The blow should break the brick cleanly in two.