A cranial flap is a piece of bone that is temporarily removed from the skull during a craniotomy, which is a surgical procedure to cut and remove part of the bone from the skull to expose the brain. The bone flap is removed using specialized tools and is replaced after the brain surgery has been completed. The bone flap is reattached to the skull with small titanium plates and screws. The bone flap will heal over time and partially heal back into the rest of the skull bone within 2 to 3 months.