Mortar the ears (the flanges on the ends of a block) of the second block and push it against the first. To butter the ears, first set the block securely on one end. Take up a trowel-length of mortar from your mortarboard and butter the ears with a downward swiping motion of the trowel. Then press down on the mortar on the inside edge of the ear to keep it from falling off when you set the block. If the mortar does fall off, start over with fresh mortar. Slice into the side of the mortar with the edge of the trowel to shape it into an inverted U. Editor’s tip: Concrete block doesn’t require gentle treatment. Grab the block by the sides of the webs and, looking down into the cores, push it into place, lining it up with the others. Don’t slide the block into place—you’ll displace the mortar and create an uneven joint. Once you have completed the wall to its finished height, fill the pilaster cores with mortar mixed slightly wetter than joint mortar so it pours more easily. You will also have to install rebar in the footing of a retaining wall and core-fill the wall for added strength. You don’t need to throw mortar on the center web. That makes the concrete block more difficult to level and plumb and wastes mortar. The only exception is when you’re placing metal reinforcement on the corners of a concrete wall. In this case, butter all the web and embed metal lath into the mortar. You can also cut and bend the reinforcement bar into a right angle and push it into the mortar. Then smooth the mortar over the reinforcement. If you don’t top your wall with lumber, cap blocks are made specifically to hide the top cores and provide a finished look. If you’re laying cap blocks, throw mortar on the top edges of the last course and lay the first cap block in the corner. Butter the ends of the remaining block and set them centered on the wall, tapping them level. Plain mortar makes an acceptable cap for a block wall, but it requires some support. Lay metal lath into the mortar before laying the last course of blocks. Lay the last course, then core-fill it, overfilling by about 1/2 inch. Level the mortar across the webs, then round its edges to let water drain off more easily.
