How to open metal piggy bank?

This article was taken from the June 2014 issue of Wired magazine. Be the first to read Wired's articles in print before they're posted online, and get your hands on loads of additional content by subscribing online.

Ever forgotten the tin opener? Here's how to open your beans using nothing more than a hard surface. "It's a technique many survivalists use," says Ryan Arter, owner of outdoor shop Mission Survivor, who can bust open a tin in just over 30 seconds using nothing more than a kerb. "I carry an opener but if this skill is needed, I will be happy that I know it."

Find the weak spot

Tins are sealed by pressing the top lid over the tin and bending the edges to form a crimp. It means there's only a small amount of metal around the top lip, which will break with enough friction.

You will need to protect your hands with gloves for this exercise, because the edges of the tin will be extremely sharp.

Select a stone

You can use the pavement in urban areas, or some kinds of rock in the wild -- quartz sandstones, quartzite, granites and rhyolites.

The harder and rougher, the better. "However, soft rocks, such as limestone, will not work," says Arter.Flip the tin upside down, so that the top of it is in contact with the rough surface.

Grind it down

Scrape the tin across the surface in a backwards-and-forwards motion. You'll see the edges wear down and gradually start to separate, and moisture from the contents will spill on to the rough surface. The time it takes to do this depends on how firm you are -- it can be done within ten seconds.