As the top of an acoustic ukulele is constantly under tension due to the strings and the vibrations caused by playing, it can deform or tear. In order to prevent this and to increase the vibration of the top at certain points, (usually thin high) bracings (struts) are attached under the ceiling, which can also connect to side and back. There are different techniques depending on the manufacturer. Bracing also compensates tension and can amplify the resonance of the instrument.