Most framing lumber is plane-sawn, meaning that it is cut roughly on the tangent or parallel to the wood grain, leaving the end grain appearance of loops and growth swirls. This is the simplest method of milling where a tree is cut square and sawed lengthwise. Quarter-sawn, or vertical grain lumber, is cut on the radius or perpendicular to the grain allowing for a uniform parallel orientation to the trees growth rings. Quarter-sawn wood is cut into quarters and then is flipped 90 degrees back and forth to saw off each board. Quarter-sawn wood maintains a straighter grain and a board that is 50% more stable. A plane-sawn board will shrink in width more and is more likely to warp than quarter-sawn boards. Quarter-sawing lumber requires more labor to produce and will be more expensive. Many species of wood display a beautiful pattern of rays when expressed with a quarter-sawn cut.