What is a process that involves taking parts from unserviceable items to maintain equipment?

The process of taking parts from unserviceable items to maintain equipment is accurately described by cannibalization. This method involves disassembling non-functional equipment to salvage usable components that can be fitted onto serviceable items, thereby extending the life of the operational equipment. Cannibalization is particularly valuable in situations where new parts are unavailable or when equipment needs to be restored quickly to minimize downtime.

Controlled exchange refers to a process in which parts are exchanged in a regulated manner, typically involving accountability and documentation to ensure that the items are replaced properly. Routine maintenance involves regular servicing and inspections of equipment to ensure its operational efficiency but does not necessarily include dismantling other units for parts. Supply chain optimization focuses on improving the efficiency of the supply chain processes and does not directly pertain to the act of using parts from unserviceable items.

Thus, cannibalization is the correct choice as it directly relates to the practice of salvaging components for maintenance purposes.