The old roof was lapped planks, with at least 4 layers of felt - pretty waterproof, but also very heavy. Here it has been cut off along the edges and is being slid off as a large panel. It weighs about the same as a person, probably about 80 kilos at least. Some careful sliding and leveraging was required..
Here is the shed looking up at the new roof through the hole in the old one.
Big panels are a bit of a health hazard. This one especially, as the clout nails that hold the felt on stick out through the wood. If it slides over you, it grates your skin mercilessly.
The same panel from the side