Mathematics is all around us. This danger sign warns you about both depth and width. What does this sign mean? What does it want you to do or not do? How do you know? Where might you find a sign like this in your suburb? How large a hole can you make before you might hit a cable? How far does this warning extend? Can you build a garden in the is area? Construct a shed? Can a council build a road in this area? Plenty to keep your students actively thinking.