A thermoplastic sheet is a moldable plastic sheet that can be easily shaped when heated and retains its shape when cooled. This durable material is commonly used in orthopedic and rehabilitation applications, such as for making thermoplastic splints or as a splinting material. Its main features include its ability to be molded to fit the specific body part that requires support or immobilization and its strength and durability once it cools and hardens. This material comes in various thicknesses, textures, and colors, making it versatile for different applications. 

In summary, thermoplastic sheets are widely used in the medical field for orthopedic and rehabilitation purposes due to their ability to be molded to fit the body, their strength and durability, and their versatility as a material for thermoplastic splints or splinting materials.