Before using the free signature, it was necessary to apply for a certificate and download it online to install third-party software that required a visa, but now it is impossible to apply for a certificate online. Only by swiping the computer can you crack the mobile phone. Another function of visa-free is that when a software is signed by others, it will appear "unable to install, certificate is limited". At this time, you need to "remove the signature" in the free sign, and then sign it with your own certificate, but the certificate production is suspended online, and the free sign only has the function of removing the signature.