Spacers are for the horizontal spaces between two or more courses of concrete blocks and serve to make laying concrete block easier. The spacer keeps the weight of the upper blocks from squeezing out mortar and helps keep each course of blocks evenly spaced for a uniformly level wall. The spacer sits atop each block and holds the blocks above it at the industry standard 3/8-inch distance. Spacers can be found at block supply companies.
Lay and Level the First Course
Apply two rows of mortar along the length of the wall footing with a trowel. The rows should be spaced and centred according to the size of block being laid. Set the first course of blocks in the mortar. Set a bubble level atop each block to ensure it is level. Apply mortar to the end of the block where a new block will be placed. Butt the new block up to this one and use a tape measure to ensure a 3/8-inch gap. Repeat this process until the first course has been laid and levelled.
Laying the Second Course With Spacers
Apply 1/2-inch of mortar along the top ridges of the first course of blocks. Place the 3/8-inch spacers down into the mortar at each block centre and joint between two blocks. Use the trowel blade to press them down flush into the mortar. Set the third course of blocks atop the spacers so that only half of the spacer is covered up by one block end and the other half of the spacer is covered up by the adjoining block end. Apply mortar to one of the block ends before bringing them together. The vertical joint gaps must be 3/8 inch.
Levelling the Second Course
Set a yardstick bubble level atop the second course of blocks. Look at the bubble. If the bubble isn't centred, press down on the top of whichever block needs to go down to centre the bubble. Repeat this levelling across the entire course of blocks. Add as many courses of block as desired.
Cleaning Up the Joints
Scrape any excess mortar away from the joints with a trowel. Run a mason's point tool along each of the vertical and horizontal joints in the wall to smooth out the mortar.