If you need to make some simple electronics repairs, but don't have a soldering iron, you aren't completely doomed. You can use plenty of other tools, along with almost any heat source, to solder whatever needs soldering.
In this video from Make's YouTube channel, Jason Poel Smith demonstrates the different ways you can solder wires and electronics without a soldering iron. Smith explains that soldering two wires together doesn't even require a soldering tool, but if you need to do some more intricate work, steel is the best choice for an impromptu tool. Steel wire, screwdrivers, nails and Alan keys are all potential tools for your emergency soldering. Just heat your wire or other steel tool over some open flame for 20-30 seconds and then proceed to solder as you normally would.
This is a more ancient approach to soldering, and you'll only be able to solder a couple of spots at a time, but it works. It's important to be careful around open flame, so take any necessary precautions. If you're completely lost when it comes to soldering, it's much easier to learn than you might think.
Soldering Without Electricity [YouTube]