Minecraft wiki entry for Nether_survival, associated text: Even though hunting, exploring, and mining may sound fun, it is unwise to start doing this as soon as the player steps into the Nether for the first time. The player's first order of business is to build a cobblestone shelter around the portal. Brick, stone, and other blast-resistant blocks also work, but cobblestone is cheapest in the Overworld. As noted above, nether brick fences can be crafted even before entering the Nether at all (by mining ruined portals for netherrack), and these are both transparent and blast-resistant.