Which of the following is an important safety rule to remember when using a crank-up tower?

Crank-up towers use a system of pulleys and winch cables to hold their telescoping inner sections at extended heights. If you climb an extended crank-up tower and the lifting cable snaps or the winch slips, the heavy tower sections will immediately collapse downward like a guillotine. To prevent severe injury or death, a crank-up tower must never be climbed while extended unless heavy-duty mechanical locking devices are engaged to physically block the sections from sliding down. Alternatively, you must lower the tower entirely so it cannot fall any further. Grounding and painting rules are general tower maintenance considerations, but they have nothing to do with the specific mechanical dangers unique to climbing a crank-up tower.