The "Teyon" (The Master Thatcher)
The man at the top of the ladder is likely the teyon. He directs the others on where to place each bundle. Notice the blue truck—modern transport has made this slightly easier, but the work on the roof itself remains exactly as it was in the Middle Ages.
A later photo will show you the material they use. The Park and owners have to train people to do this. I think it would be an interesting project. I think it might be kind of fun to stay in one while working on others... as long as I had some good wine and cheese.