A shoulder rivet works by separating the fastening area from the functional working area of the part. During installation, the rivet end is formed to lock the assembly together, while the shoulder section remains as the controlled contact surface for rotation, spacing, or location. This makes shoulder rivets especially useful in assemblies where a standard rivet would create too much compression, insufficient clearance, or unstable movement. In custom designs, the relationship between shoulder size, body length, and rivet forming section is developed according to the real assembly structure and motion requirement.