Within our cemeteries, it is common to find among different symbols objects that may reflect either the profession of the buried person, or act as a reference to their affiliations or membership (i.e. Freemasonry). They may also represent their hobbies, leisure or fields of interest.
A hammer is often found on graves of carpenters, though it may also be used to symbolise the power of creation.
A hammer crossed with a sickle, however, would obviously have a communist meaning.