Batter boards are temporary frames that establish the outline and angle of a home foundation. Typically, they consist of a pair of horizontal boards nailed to posts set at the corners of an excavation. The batter boards indicate the proper location, level, and angle of the structure, and serve as a fastening place for stretched cord to show the outlines of foundation walls.
Used for reference during the initial excavation and rough grading phases of construction, most batter boards consist of 2x4 stakes driven into the ground (usually by sledgehammer) with a crosspiece of 1x4 nailed or screwed across them in a shape that looks like a running hurdle. For especially tall foundation construction, batter boards should be braced with some kind of support to maintain the integrity of their angles.
Despite their temporary nature, the exact position of batter boards is highly significant to pouring an accurate foundation. The vertical pieces need to be stable, but don't have to be set at a particular angle. The horizontal elements, though, must be exactly level with each other. Otherwise, the concrete will set unevenly, throwing off the dimensions of all following construction steps.
Batter boards should not be confused with batter walls, an architectural term meaning walls that slant slightly in toward the center of a structure.