Your character is able to attach Firewood to a Fireplace Kit that is still in the Inventory. Combining those two items in your inventory allows you to save a lot more extra space, without having to manually carry wood to a campfire.
This allows your character to deploy an Ignite-ready Fireplace without having to look for wood after setting it on the ground.
Related to http://feedback.dayzgame.com/view.php?id=17828 issue. Combining the two allows you to carry a Fireplace Kit inventory with additional 1 piece of wood and 8 Stones attached to it.
Screenshot #1 - Attaching Firewood to a Fireplace Kit in my inventory.
Confirmed, this also works with a rock. You can attach them both to your fireplace kit and have a stone ready to repair axes with ready to go. All with the convenience of one 2x4 slot :)