The BackTools Mod adds a feature which makes it possible to carry tools on your back. You can carry everything from pickaxes to swords. Not only does it look totally badass but it is also quite useful as it frees up one slot in your inventory.

How does it work?
To carry a tool on your back simply hold the item in your hand and then tap on the ground to place it on your back.
Here is a list of tools which you can carry :
Swords,Pickaxes,Axes,Bow, Sticks