A bokken, which is a wooden sword used in Japanese martial arts training, has the potential to cause serious injury if used with enough force. While it is possible for a bokken to crack a skull, it would require a significant amount of force and a direct impact to a vulnerable area.

It's important to note that using a bokken or any weapon in a dangerous or violent manner is highly discouraged and can result in severe harm or even death. Bokken training is typically conducted in a controlled environment, with an emphasis on discipline, technique, and respect for the safety of all participants.

If you have any concerns about safety or are considering using a bokken for any purpose, it is advisable to seek proper training and guidance from a qualified instructor in a recognized martial arts school.