Foundations Course Instructor, Abel Dances marked this log to show lumber cuts and wood movement. Starting with the center of the log, the circle shows the heart or pith. Look low and to the right, you'll see marks that indicate quarter sawn. Above the heart are horizontal lines showing flat sawn. Between flat sawn and quarter sawn are vertical growth rings. That's vertical grain. Lastly, is the color of the wood. The sap wood is yellow and the heart wood is orange.