Occasionally, trees produce wood with a wavy grain, greatly increasing the value for decorative veneers. The wood is a medium weight for a hardwood, weighing 630 kg per cubic metre. It is a traditional wood for use in making the backs, necks and scrolls of violins. The wood is often marketed as rippled sycamore. Whistles can be made from straight twigs when the rising sap allows the bark to be separated, and these, and sycamore branches, are used in customs associated with early May in Cornwall. The wood is used for fuel, being easy to saw and to split with an axe, producing a hot flame and good embers when burnt.