Step 2 · Establish Vanity Centerline
Determine the total space allocated for the vanity. Measure this space and find its center point. Use a tape measure to measure the width of the space and divide by two to find the center. Mark this center point on the wall at a convenient height. Then, use your level to draw a light, plumb (perfectly vertical) line through this mark. This vertical line is your vanity's centerline and will be the primary reference for all subsequent horizontal measurements for the sink, drain, and water supplies.