Which items do Cebus capuchins use as hammers and anvils?

Stones as hammers and logs as anvils to crack nuts.

The intelligence of Cebus capuchins is often evidenced by their documented tool use, which aids them in processing difficult food sources. Specifically, researchers have observed them utilizing natural objects for mechanical advantage. They employ stones to function as hammers when attempting to break open hard-shelled items such as coconuts. Conversely, they use logs or similar stable objects that serve as anvils upon which the hard items are struck to facilitate cracking and access to the contents, including hard-shelled invertebrates like snails.