Use of a 
Standard Aggregator or an 
Advanced Aggregator will open the Aggregator Interface.
The Aggregator Interface will allow you to merge 2 items of the same type and slot into a single item. The new item will inherit the appearance of one item, but the attributes of the other. Both items must be for the same Slot (e.g. Waist), of the same Type (e.g. Cloth), and of the same Category (Armor or Weapon).