Minecraft wiki entry for Shelters, associated text: By making four three block high walls around you, you can simply hide from most mobs. Adding a roof (at the third block, that is 2 blocks high inside) protects against endermen (which can't fit) and spiders, which can otherwise climb the walls. You can make this out of almost anything—cobblestone is more secure, you can use wood planks if you have enough, but even dirt will do in a pinch. You need 13 blocks as a bare minimum (four 3-block high pillars around a 1×1 refuge), but two or three times that, or even a whole stack of 64, lets you build something you can actually move around in, and do some crafting and smelting overnight. (Note that you can use the crafting table and/or furnace as part of the walls.) Keep a block or few in your inventory as spares, in case of enderman theft (see below). You have two main risks: One is spiders, which can both sense you through the walls, and climb the walls. However, they can't fit through small holes, and if you make a roof with only a one-block hole, spiders can't get through (but you can still tell when day returns). The other hazard is if an enderman wanders by and takes a block out of your shelter. Wait for the enderman to wander away a bit, then replace the block, with one of your spares, if possible without letting your cursor cross the enderman (“looking at them”). When full daylight comes, mine a door in your wall, and exit. Keep a wary eye out for monsters, and in particular be prepared to run very fast away from creepers.