To see a sledgehammer, when you are dreaming, can be interpreted as symbolism of psychological barriers around you. These obstacles are artificially created by yourself. In the dream to use a sledgehammer works as a trigger to break down these artificial barriers.
Dream dictionary: sledgehammer dream meanings
To dream of using or seeing a sledgehammer, offers to remove the barriers you have made for yourself. Maybe there is a fear to do so, however, after removing them you will be able to accomplish things much easier.
Seeing a sledgehammer in your dream suggests you should get out of isolation.