How to Install a Wall Cap

Set the first wall cap on one of the retaining wall's ends. Most wall caps have one rough edge and three smooth edges. Position the cap so the rough edge faces the front of the retaining wall. Mark the smooth edge on the end of the retaining wall using a piece of chalk.

Measure 1 inch in from the smooth edge in two places and mark the cap with chalk. Line up a level with the two chalk marks and trace along its edge with a piece of chalk. Flip the cap over and repeat this step.

Hold a 1/2-inch chisel on a chalk line. Tap the chisel's handle with a hammer to make a score line. Score the chalk line's entire length, then flip the cap over and score along the chalk line on the other side. Make score lines on the cap's side edges connecting the two long score lines you just made.

Lay the cap on a flat surface. Position the 1/2-inch chisel in the center of the scored line. Hit the chisel's handle firmly with a hammer to break the cap's smooth edge off and create a rough edge.

Place a tube of landscape adhesive in a caulk gun and cut off the tip with a utility knife. Place two parallel beads of caulk along the retaining wall's top level where the cap will go. Set the cap in place and adjust it so the edges extend about 1 inch past the retaining wall.

Apply two more beads of construction adhesive on the retaining wall next to the cap you just installed. Set a second cap in place. Pull it forward so its front edge is equal to the first cap's front edge, and press the two caps' side edges together. Continue to set caps in place all the way down the wall.

Measure the distance from the last full block to the end of the retaining wall and add 1 inch. Break a cap to this length the same way you broke the first cap. Glue this final cap in place with landscape adhesive.