There are 7 pulleys in the flap system. Each needs a cable guard and each cable guard needs to be fastened to a frame member or strut so it can't rotate and bind the cable. They are conceptually simple but I have struggled with making them accurately enough so they are effective, don't rub and anchor effectively. It's a bit of a special challenge and metal work is rather new to me. After many false starts and ruined cable guards, I now have 4 of them completed. It's fine, but I know that some people could knock one off in 15 minutes. I hope I am getting better at this, since there are a bunch more in the rudder and elevator trim system. And two more in the other wing which have yet to be mounted.