<Ul> <Li> Areas of weakness on the tile are fewer since no holes have to be drilled </Li> <Li> Roofing features such as valleys and domes are easier to create since narrow tiles can be used </Li> <Li> Hook fixing is particularly suitable in regions subject to severe weather conditions, since there is greater resistance to wind uplift, as the lower edge of the slate is secured . </Li> </Ul> <Li> Areas of weakness on the tile are fewer since no holes have to be drilled </Li> <Li> Roofing features such as valleys and domes are easier to create since narrow tiles can be used </Li> <Li> Hook fixing is particularly suitable in regions subject to severe weather conditions, since there is greater resistance to wind uplift, as the lower edge of the slate is secured . </Li>

What property would you need in a rock used to make a roof