A shoulder rest is an accessory used by string players, such as those who play the violin or viola. It attaches to the instrument's body and rests on the player's shoulder, providing support and stability. This helps musicians maintain proper posture and reduces strain during long practice sessions or performances. Shoulder rests come in various shapes, sizes, and materials, allowing players to choose one that best fits their comfort and playing style. They can enhance sound quality by improving the instrument's resonance and can also help prevent injuries related to improper positioning while playing.