Minecraft wiki entry for Beginner%27s_guide, associated text: To get in and out of a shelter, the player needs some type of entrance/exit. If necessary, the shelter's exit can simply be some dirt or other easily broken blocks. A much better way to set up a shelter's entrance is by crafting and placing a door. A door is relatively cheap and can be placed on any solid, opaque block. The door requires a vertical space of two blocks, similar to how a bed takes up a horizontal space of 2 blocks. Placing the door from the outside causes it to be flush with the outside wall. Doors can be quickly opened and closed and while closed some of them allow the player to see outside, without monsters being able to see or attack the player inside. In Easy and Normal difficulty, zombies bang on doors, but cannot actually break them down. If you are playing on Hard difficulty (again, a beginning player shouldn't be!), a zombie can break down a wooden door, but even then, you can easily block off the door from the inside with one or two blocks.