When soldering by hand, it is easy for a small accident to happen. Suddenly hot solder flows over the PCB. To prevent wasting time and money, solder resists or covers protect the PCB reliably against slip-ups. Solder resists generally offer protection against corrosion and mechanical damage and improve the electric strength of the board, for example. You must ensure that the solder resist is compatible with the flux and other substances that may be present.