Saddle Bag

A horse can be used to transfer loot in or out of a base through the use of saddle bags.

Tutorial

 * 1) Equip your horse with saddle bags.
 * 2) Find a part of the base in which the horse's head will clip through and your teammate can access.
 * 3) Use the horse's inventory to transfer loot.

Video Tutorial
The tutorial is only part of this video and has been linked to only the relevant section.

Tips

 * This may come in use if you or a teammate has gone "deep" but has gotten trapped inside.