Diodes are in use for electric locks, strikers, relay coils, rectifying ac power.
The diode use for discharging the back-current of coils and eliminate the damage of electronic circuits and contacts over time
Diodes are in use for rectifying, dumping pules, rectifying and many other applications
The 1N4007 is a general peruse diode:
Max (revers) Voltage: 1000V
Max (forward)current: 1Amp