Here are the steps to cut backer board:
1. Lay the backer board on a flat surface like a concrete floor or work table.
2. Using a straightedge, run your utility knife or scoring tool along the line to make a groove.
3. Repeat this step two or three times to make the groove deeper.
4. Once you have a deep enough groove, lift the board to an upright position and press your knee against the lines.
5. Press down on the board with your knee and snap it along the groove.
