Step 1
Drive a stake or rod at the base of the retaining wall. Set it deep enough that it will remain vertical on its own.
Step 2
Level the stake on all sides. Put the level flush against the side of the stake to confirm that it is truly vertical. Adjust as necessary to make it so.
Step 3
Mark 1 foot from the base on the stake with a marker. Make sure to hold the tape measure tight against the stake when measuring.
Step 4
Tie a string or line to the stake at the one foot mark. Attach a line level to it if you have one.
Step 5
Hold the string level to the face of the wall. Measure the distance of the string between the stake and the point on the wall where the string is level. This is your batter ratio. For example, if the string is 2 inches between wall and stake, your batter ratio is 2:12, or 1:6.
Step 6
Continue the steps as necessary up the stake at 1 foot intervals. The batter may vary, so you may want to get an average.