The BackTools Mod allows you to carry a tool on your back. You can carry anything from swords to pickaxes. Not only does it make look totally radical but it is also quite useful as it basically gives you 1 more inventory slot.
All credit goes to MrElectric
How does the BackTools Mod work?
To put a tool on your back simply hold the item in your hand and then tap on the ground to put it in your back. To hold the tool in your hand again press the B button on the right side of the screen.
Here are the tools that you can carry on your back (more will be added in future updates):
This is an early release of the mod so it is not perfect. It will no doubt be buggy. But it is definitely useful as it will grant you one extra inventory slot when you carry a tool on your back.