SERE Central offers the best most natural fat wood you can find. Our Fat Wood will light and burn under the most extreme conditions. We select our Fat Wood for maximum burn time and test every batch. We search for resin content of 80% or above. What is fat wood? Fatwood, also known as "fat lighter", "lighter wood", "rich lighter", "pine knot", "lighter knot", "heart pine" or "lighter'd" [sic], is derived from the heartwood of pine trees. The stump (and tap root) that is left in the ground after a tree has fallen or has been cut is the primary source of fatwood, as the resin-impregnated heartwood becomes hard and rot-resistant over time after the death of the main tree. Other locations, such as the joints where limbs intersect the trunk, can also be harvested. Although most resinous pines can produce fatwood, in the southeastern United States the wood is commonly associated with longleaf pine (Pinus palustris), which historically was highly valued for its high pitch production.