Are fitters and senior workers useful?

Of course it works. Junior, intermediate and senior technicians, such as senior technicians, are very scarce on the Internet, and they are "golden blue collar".

Vocational qualification certificate is the proof that workers have the necessary knowledge and skills to engage in a certain occupation. It is the qualification certificate for workers to apply for jobs, take up posts and start businesses, the main basis for employers to recruit workers, and the effective certificate for overseas employment and foreign labor cooperation personnel to notarize their skill level.