Final answer:
The tool used for placing flex blocks out for acceptance and tracking acceptance of flex blocks is called the Flex Control System (FCS).
Step-by-step explanation:
The tool that is used for placing flex blocks out for acceptance and tracking acceptance of flex blocks is called the Flex Control System (FCS). FCS is a software tool that is used to manage and track the movement of flex blocks within a transportation network. It allows dispatchers to assign flex blocks to specific flex drivers and monitor their acceptance and completion status.