How can I make a tool go on your back when you unequip it?

I've seen games where when you unequip a tool it goes on your back, and when you equip it, it goes away. Can someone help me with this?

You replicate the tool to the character and weld it onto its back;

Welding

Check if the tool was unequipped

Replicating the tool

There's a really nice tutorial on animating tools which you can find here

Make it so that once you unequip the tool, you play an animation to make it look like the tool's on your back.

Also, make sure you play a different animation when you equip it, or else once you unequip and then re-equip it the animation would be stuck.

You don't need to replicate the tool, whereas just rig it.