Unlike cursed tools, cursed objects are not items imbued with cursed energy, but actual curses bound to the form of a jujutsu artifact. These relics are often leftover from the past eras of the jujutsu world or are the remains of powerful curses and sorcerers. This also includes paper talisman and other sealing methods called Constraints that contain curses as a means to seal other cursed objects.
Cursed objects can leave residual cursed energy just like normal cursed spirits. Special grade cursed objects cannot be destroyed with jujutsu and certain ones can be used to incarnate powerful cursed spirits. In Sukuna's case, his fingers can choose its host and have such a strong presence that they can still attract curses. Once Sukuna was fully reincarnated by Yuji, all of his fingers resonated with cursed energy, resulting in the empowerment of several different curses.
Infant cursed spirits such as cursed wombs can also be considered cursed objects. While Dagon was a sentient spirit while still existing as a cursed womb, his power was very limited compared to his fully realized cursed spirit form. He was able to advance his form through emotional trauma, ascending to a much more powerful state.
The Cursed Womb: Death Paintings were cursed objects created under special circumstances, sealed with a constraint for 150 years. Death paintings could be incarnated with any vessel, unlike Sukuna's fingers.
Among other artifacts are items that can erect barriers such as Commissioned Curtains or Prison Realm. The former is a common item used by curse users that appears to be wrapped in constraints, allowing the user to program special conditions into a curtain before it is activated. Prison Realm is the remains of a sorcerer monk from a past era, a literal living barrier capable of sealing absolutely anything.