Spine boards are typically made of wood or plastic, although there has been a strong shift away from wood boards due to their higher level of maintenance required to keep them in operable condition and to protect them from cracks and other imperfections that could harbor bacteria. Backboards are designed to be slightly wider and longer than the average human body to accommodate the immobilization straps, and have handles for carrying the patient. Most backboards are designed to be completely X-ray translucent so that they do not interfere with the exam while patients are strapped to them.