A simple mod which adds two key binds, Main hand, and Off Hand. This will allow you to specify exactly which hand you want to use to preform an action.
This doesn't not affect the original key-bind, you must switch to use the new key-binds to make use of this mod.
Remember to un-bind the other hotkey, ( escape sets it to "NONE" )
Must be installed on server and client.
Can I use this in my mod pack?
Is this a Client Only Mod?
No, you must have it installed on the server and client.
You can install it on the server without forcing players to use the mod however, since they must still adjust their key binds to make use of it, and it doesn't change any default behavior.