Complex sentence: A strip of wet rawhide would be stretched tightly around the forehead of a bound victim and when exposed to sunlight the material would shrink; as the material dried and if left unattended, the victim's skull slowly cracks as a result of the pressure.
Split into simpler sentences: A strip of wet rawhide would be stretched tightly around the forehead of a bound victim and when exposed to sunlight the material would shrink. As the material dried and if left unattended, the victim's skull would crack as a result of the pressure.