NOT KNOWN FACTS ABOUT SOLAR WIRING HARNESS MANUFACTURER

With Daisy Chain you get a regular wiring, when Leap Frog will save revenue on wire and cuts down power losses produced by warmth, staying the most efficient wiring method. this is the dumb dilemma but I’m not solar panel savvy. What do the rubber plugs at the conclusion of solar panels do? Are they vital? I have three that are lacking and I h