Explanation:
A vertical lifeline allows the worker to move up and down the entire height of the line rather than having to disconnect and find a new tie-off point on the tower or ladder he or she is climbing. Workers connect to the lifeline by a "rope grab" deceleration device that travels along with the worker as he or she moves higher or lower.
A worker using a vertical lifeline can travel up & down along the height of the line. This way s(he) does not have to disconnect & look for a new tie off point on the ladder or tower s(he) is climbing. A "rope grab" deceleration device connected to the lifeline is used in this case. This device moves with the worker as she or he travels lower or higher.