A hammer is both a creative and a destructive force. It can be used to build things, and it can be used as a weapon.
If you dream about a hammer, you could be looking for the tools that you need to solve a problem in your life. You should examine your strengths and consider how they can help you.
Hammering nails in a dream can mean that you need to integrate different parts of your personality in order to become a more well rounded person.
A dream that you beat someone with a hammer can be a sign that you are repressing feelings of anger. Your dream could be telling you that rather than repressing your anger, you could find a constructive outlet for it.
If you dream that someone else hits you with a hammer, you could be feeling guilty about something. You may feel that you have created something that has been harmful to yourself or to others around you.
A double-sided hammer in a dream can represent the distinction between vengeance and justice.