A hammer with a loose head can be safely used after securing the head with duct tape.

Using a hammer with a loose head can pose significant safety risks, regardless of any temporary fixes like duct tape. Securing the head with duct tape does not eliminate the possibility of the head detaching while in use, which could result in injury either to the user or to others nearby. Hammers are designed for striking, and their heads need to be securely attached to ensure they can deliver force safely and effectively. Relying on duct tape compromises the tool's structural integrity and can lead to a failure, making it unsafe to use. True safety requires that all tools function as designed, without makeshift repairs that may not hold up under use.