Customize

A process by which an item is made to be usable only by one character in the game. This applies to Weapons and Armor:
 * Weapons are not customized by default but can be taken to a weaponsmith (marked with [Weapons] in towns and outposts) and customized for the very low sum of 10 Gold. Customizing a weapon has its benefits: The weapon will deal 20% more damage. On the flip side, customizing a weapon means you will have a very low chance of selling it to other players. Customized weapons can still be salvaged for Upgrades.
 * Armor is always customized. When you purchase a piece of armor it will be customized to your character automatically. As such, armor purchased from other players can only be used for salvage.

If you hover your mouse over an item you can tell if it is customized. Customized items will have a note in grey at the bottom of the description that states that they are customized for a specific player.

''Tip: Customize the weapons you plan on using regularly. Not the ones you are just trying.''