Size the trench so there's enough room for the retaining wall block and at least 8 in. of space behind it. Excavate deep enough to completely bury at least one full course, including space for 6 ...

Retaining walls serve both a practical and decorative ... to wet your wall from top down to dislodge dirt. Afterward, spray on a mix of dish soap and water (about 1 squirt per 2 gallons).