Minecraft wiki entry for Pillar_jumping, associated text: Players can also build a pillar out of a flammable material such as wood or wool, then ignite it when it is no longer wanted, however this presents a number of problems. First is the possibility for unintentional spread of fire. Another is the fact that a block lit on fire is not guaranteed to burn away completely, which can lead to burning wooden blocks suspended high in the air (although this problem has been mostly resolved since the release of Beta 1.3). Since Beta 1.6, using fire to burn very high pillars is not recommended, as it can stop midway due to the nerfed fire.