Final answer:
In assisting a client with limited mobility to turn in bed, a nurse would place an additional pillow supporting the client's back to maintain proper alignment and prevent rolling.
Step-by-step explanation:
After successfully turning a client with limited mobility to the side, a nurse would place an additional pillow supporting the client's back. This practice is known as the side-lying position or lateral position, and it helps maintain proper alignment and prevents the client from rolling onto their back or stomach. The pillow supports the natural curvature of the spine and keeps the client in a stable position which is crucial for comfort and to prevent the development of pressure ulcers.