Has anybody used a thin layer of sand over the top of your compacted gravel base to create a level setting base for retaining wall block? I always used a little bit of the fines from the grade 8 gravel but I saw a guy screed a really thin layer of sand on top of the gravel. If you have done this how has it worked out. Any problems in the future? Do you just tamp with hammer to set them? How deep do you normally have the sand?