A wooden frame or board with a plumb bob attached, cut to the specific angle of a retaining wall's slope. Masons use it to ensure the face of the wall leans into the retained earth at a consistent angle, rather than going straight up. This inward tilt adds structural stability against soil pressure.
Heard on the job
Grab the batter rule so we can check the pitch on this retaining wall before the mortar sets.
Insider tip
Older masons often build their own batter rules for specific jobs, cutting the exact pitch needed for the site directly into a scrap piece of lumber.