You can use cement blocks to build an economical pillar as part of a foundation, the end of a fence or an indestructible mailbox post. Concrete blocks are manufactured to be slightly smaller than eight inches square by 16 inches long; when the proper mortar joint is added, you're left with an easily workable eight by 16 inches. You can buy cement blocks with flat ends or inset ends; buy the ones with flat ends to build a good-looking pillar. These instructions are for a 16-by-16-inch-square pillar.
Lay a level onto the footing or foundation where you're building the pillar to be sure its base is level. If you are pouring a new footing, put some rebar in it to make it stronger.
Sweep the surface clean and wipe it with a damp cloth. Mark the exterior lines of the pillar using a pencil. Gather all of your necessary materials before you start. Buy a bag of mortar for every 40 blocks, plus three more bags for filling the holes in the centre of the blocks. Divide the height of the pillar by four to determine how many blocks you need. Because each block is eight inches high, and you need two blocks for each course, you will need two blocks for every eight inches of height. If you're building a 64-inch pillar, you will need 16 blocks.
Open a bag of mortar and empty it into the wheelbarrow. Add small amounts of water until you achieve a consistency that is workable but not soupy. It should be roughly the consistency of peanut butter.
Apply a 3/4-inch-thick layer of mortar on the base where the first course of blocks will be laid. Put a block in place and tap it firmly with the trowel handle. Line up the edges of the block with the lines on the foundation or footing. Lay a torpedo level on top of the block and ensure that it's level in both directions.
Spread mortar on the side of another block and push it simultaneously against the first block and into the bed of mortar on the bottom. Check this block for level, then check both blocks together by laying a 4-foot level across them.
Spread more mortar on the block tops, then lay another course of two blocks on top of the first two so that the joint between the two blocks in the first course is perpendicular to the joint between the two blocks in the second course. Check that the sides of the column are plumb using the 4-foot level, then check that the top of the second course is level using the torpedo level.
Continue laying blocks in this manner, continually using your levels to be sure the column is level and plumb in all directions. When your pillar reaches a height of three or four feet, fill the holes in the centre of the blocks with mortar and tamp it down. This will make your column much stronger.
Add courses of blocks until your pillar is the right size, filling the holes in the middle with mortar at three- or four-foot intervals.