The Finish to Finish dependency forces a task to finish only when/after its predecessor/successor is completed; both tasks finish at the same time. If a nonzero lag is present, it is added to the Finish date.For instance, a value of 4FF+2 days in the Predecessors column signifies a Finish – Finish type link with a lag of two days, where the current task has the task with ID = 4 as its predecessor.