Check for straightness and level

Set the next block in place and push it against the first block so that the joint between them is about 3⁄8 inch. Check the block for level.

Scrape mortar onto the flanges of the laid blocks and set the next course of blocks on top. Start the next row with a corner block or a half block, so the blocks will be stacked one on top of two. Check this row for level and see that the blocks form a straight line. Scrape mortar from the joints as you work.