"Home-Brewed" Battery + and - Terminal Blocks Finished Photos Added

On the subject of zener diodes, while a zener clamps for the rated voltage when reversed biased, it also conducts as a diode in the forward direction, so a blocking diode needs to be placed in series to block flow, for normal energization of solenoid coil. There are modern components that are single devices that incorporate the features, however the packaging is most often surface mount in small rectangular packages.