A cervical cap is a small, dome-shaped device made of silicone or rubber that fits snugly over the cervix. It is used as a form of birth control to prevent sperm from entering the uterus during sexual intercourse. The cap must be inserted before sex and can be left in place for up to 48 hours. To be effective, a cervical cap should be used with spermicide, a chemical that kills sperm. It is important to consult a healthcare provider for proper fitting and usage instructions, as the effectiveness of the cap can vary based on individual factors, including body type and previous pregnancies.