When you are out in the woods, it's always important to have a few survival devices, like an emergency whistle. If you forget to pack one, here's easy it is to make one with a metal can and a nail, which you probably already have with your camp gear. If you don't have a can lid, just look for something metal and pliable lying on the ground around you
After a simple conversion, you'll have a whistle that people can hear for miles. This video from Specific Love Creations has all the instructions.
Of course, when you are making one of these whistles, keep in mind that the edges of the can lid can be sharp. Dulling down the edges may be necessary before you start trying to work it into the shape of a whistle.
This is a handy trick to remember in case you're ever in an emergency and stranded in the woods. It could wind up saving your life.