This command will allow you to sneak off the edge of blocks, and create a bridge under you! Just sneak to the edge of a block that is up high!
The source code could not be found for this command!
How to use
Give yourself a command block with /give @p command_block. Place it then paste the command from below into it. One command creations are similar to Minecraft mods, but are much easier to add to your world!