Minecraft wiki entry for Beginner%27s_guide, associated text: The ⇧ Left Shift key makes you "sneak". While sneaking, your viewpoint gets a little lower, and you move more slowly. The benefit of sneaking is that you cannot fall off the edge of a block; in fact, you can sneak slightly over the edge of a block, to look at and interact with the side of the block you're standing on.