11. Some extension ladders have spikes attached to the side rails. 12. If you have a high roof, you'll have to set up an extension ladder . 13. They just can't be on a 20-foot extension ladder . 14. Of course, you will have to erect an extension ladder to get at the roof. 15. The protesters from the environmental group Greenpeace used an extension ladder to reach the roof. 16. Henry Quackenbush patented the extension ladder in 1867. 17. I was carrying an extension ladder , trying to go between the cars and stepping over some junk. 18. Each craft also carried tubular-steel extension ladders made up of light, four-foot sections suitable for quick assembly. 19. You will have to raise an extension ladder to paint the upper story or clean the gutters. 20. Using a stepladder requires the same precautions as with an extension ladder , with just a few modifications.
