Which of the following is a common material used in custom orthotics?

Plastic is frequently used in custom orthotics due to its versatility, lightweight properties, and ability to be molded for a personalized fit. It can be shaped to conform to the contours of the patient's foot, offering specific support where needed. Additionally, plastic can provide structural support while still allowing some degree of flexibility, which is crucial for comfort during use. It is also durable, which makes it suitable for various types of orthotic devices.

Wood, while historically used in some orthotic applications, is less common today due to its weight and lack of flexibility. Metal can be used for certain types of orthotics, particularly in braces or supports that require rigidity, but it is not typically used for custom foot orthotics. Fabric may be utilized in cushioning or covering layers but does not usually serve as the primary material for the supportive structure of custom orthotics. Thus, plastic stands out as the most suitable and widely used material in creating effective custom orthotics.