What is meant by “100% tie-off” regarding tower safety?

"100% tie-off" is a fundamental tower climbing safety concept that means a climber's body is continuously connected to the tower or a fall-arrest system at all times during a climb. To achieve this, climbers typically use a safety harness equipped with a dual-leg (Y-shaped) lanyard. When the climber needs to move past a structural obstacle, they can unhook one lanyard leg and reattach it above the obstacle while the second leg remains securely anchored to the tower. While securing tools, ropes, and disabling electrical panels are all valid safety practices, the specific term "100% tie-off" strictly applies to the climber's physical attachment to the structure to prevent a fatal fall.