When wiring up a multirotor, you often find that there is a need to splice some very heavy gauge wires together (like connecting 4 ESCs to a single wire to go to the battery).
If you twist all those wires together to solder them, you have a big mess. The wires are so large that you need to strip at least 1" of insulation off the wires just to get enough bare wire to make one "wrap". And one wrap is barely enough to get them to hold together. And if you move them, they fall apart. Not to mention that the resultant connection looks like a knot and is as big as a marble.
So what is the solution? Buy a spool of solid 28Ga or 30Ga Kynar-insulated solid wire - also known as "wire wrap wire" and strip off the insulation from a piece 5" or 6" long. Put the ends your heavy gauge wires together - just lay them side-by-side. Don't twist them together. Now take the 30Ga wire and wrap it tightly around the bundle to hold everything together. If it makes things easier, wrap your 30Ga wire several times around just one wire. Now lay the second wire next to it and wrap both wires. Add a 3rd and wrap and a 4th and wrap ... Solder.
Now you have a neat, well-soldered connection.