A Spirit Level is a tool used to indicate how parallel (level) or perpendicular (plumb) a surface is relative to the earth. A spirit level gets its name from the mineral spirit solution inside the levels. Typically, the vials in a spirit level are a yellowish-green color with additives for UV protection and maximum performance in temperatures ranging from -20 degrees F to 130 degrees F. Take note of where the bubble is inside the spirit tube. If it’s centered between the lines on the tube, your object is level. If the bubble is to the right of the lines, your object slopes downward right-to-left. If the bubble is to the left of the lines, your object slopes downward left-to-right.