Check base material with a level or measure down from a leveled string line. Add base material to low spots. Repeat compacting.
Add wooden shims if necessary.
Check posts for level and plumb before nailing. Use the 4 pound sledge to hammer 60d wall tie nails through the top of the post into the course below. Install the wall tie nails every 16 inches. Install full length posts to complete the course cutting only the end post.
Dig a T shaped trench behind the wall. Build the T-brace horizontally behind the wall with 4x4 posts. Incorporate the base of the T-brace by nailing it flush in between two posts in a course of the wall. Hammer rebar down through the T-brace into the ground. Bury the T-braces. Locate all T-braces below the top of the finished wall so as to not become disturbed or visible.
