"A drill." He hadn't thought about this question before but the answer came easily enough. There was really no other option. "With a drill and some perseverance even a normally weak person can break through any obstacle."

Since that answer came easily he could direct some thought to the puzzle of Haruno-san's. His first thought when it came to nails was that they were piercing and could make a good weapon, if used with precision. But if she was interested in a weapon, there were still better options. The same with a drill, certainly it could hurt someone, but that sounded like a really shallow objective. So maybe that meant... "Could it be... Are you the type that likes to make sure things hold together?"