I am currently building over my garage and I am at the stage of setting out my roof battens for tiling. I am using the tiles that I took off the garage roof which are Hardrow. When reading about fixing I see the advice is to nail every 3rd row but I don’t remember any of the old tiles being nailed. The nails hooked over the batten instead of physically being nailed into the batten. Is this right or have I imagined it ?