A fuel ladder is a term for live or dead vegetation that allows a ground-based fire to climb up from the forest floor into the tree canopy where it is more intense and difficult to fight. An overcrowded understory of grasses, shrubs, small trees, low-lying branches and dead standing timber can all be part of a fuel ladder. Thinning, pruning and the removal of excess vegetation from the forest floor can help stop the progression from ground fire to canopy fire.