Always walk on the screw heads - especially on a fibre or asbestos roof...
Many years ago (when I was 15) I worked weekends on a dairy farm. One day I was using the farms loadall to push muck out into the lagoon - it was full and so took quite a lot of effort. In my haste (and in-excperience) I pushed the boom right out, and managed to get it hooked behind the brick corner of a cubical shed. Needless to say, it did quite a lot of damage trying to get the loadall back out, and I ended up smashing some of the roof pannels.
Trying to be a good employee (and right my wrong), I immediately found some spare sheets and set to work replacing the damaged ones. Working up on the roof (which was asbestos) I made sure to only stand on the nail heads - ensuring there was always a beam under me. Unfortunately when I finished I stood back to admire my handy work - stepping off the screw heads and falling straight through the abestos sheet roof. :banghead:
Luckily the fall was only 15 feet or so, and somehow I managed to miss the cubical frames below, instead landing on the straw bedding. Needless to say it was a mistake I'll never make again - I always use crawl boards when working on fibre roofs now.
Oh - and my boss was not at all hapy that I fell through the roof - he couldn't work out what I was doing up there in the first place as I didn't dare tell him about the loadall fiasco :ashamed: