<human>:  Why did the robbers use a sledgehammer to break into the safe in the movie ‘The Great Train Robber?
<bot>: The safe was made of steel. Steel is hard. A sledgehammer is a heavy hammer. A sledgehammer is used to pound things into smaller pieces. The robbers could have used a crowbar, but the crowbar is not as strong as a sledgehammer. A sledgehammer is also very noisy.