How can flushness of fasteners be inspected effectively?

The most effective way to inspect the flushness of fasteners is through a direct visual check. This method allows the inspector to observe if a fastener is siting correctly, providing an immediate assessment of whether the fastener is flush with the surface it is installed on. Inspecting visually enables the detection of small discrepancies that might not be evident through other methods. Furthermore, a visual check can help identify any surface irregularities that could affect the fastener's performance.

While other methods like using a level, measurement tools, and tapping lightly can be useful in certain scenarios, they do not offer the same level of immediate visual clarity for assessing flushness. Measurement tools can provide precise data but might not be as straightforward for quickly identifying issues related to flushness. Tapping lightly may indicate whether the fastener is secure but does not accurately determine flushness. Therefore, a direct visual check remains the most effective means of verifying flushness.