I’m replacing a slate on a sark boarded roof – does the HallHook work?

It depends on whether the nails are in the right position. On a battened roof the nail holes are determined by the battens. On a sark boarded roof, the nails should be in the right position but they could be in a different position.

If the nails are not in the same position on a battened roof, then the HallHook can’t work effectively as the lap could be compromised.