When you grow up on a farm or homestead you learn so many things that become so second nature that you just can't remember not knowing how to do them. One of the many things I learned, at least I assume I learned it, as a child is using acorn caps to make a whistle.
Like so many things in life, I took that knowledge for granted and assumed that everyone knew how to do this. Imagine my surprise when I found that not one of my coworkers knew how to do it. I spent a week teaching one after another to make the whistles, having quite a laugh at their initial efforts, until in the end each one could make a sound as loud and clear as my acorn cap whistle.
Acorn caps make a loud shrill sound, and if lost in the woods, the sound will carry farther than the standard search and rescue whistle. Caps are relatively easy to locate in areas with oak trees and best of all they are free. Most acorn caps will last a few months if carried all the time, unless efforts are made to preserve them. I've never preserved mine so I'm not sure how the preservative will change the sound.
When choosing an acorn cap one should choose a cap that is of a size easy enough to hold, strong, with a relatively smooth and level rim. A cap that is no bigger than a quarter but larger than a dime are the easiest to hold and work with. A nice deep cap will give maximum sound.
Holding the cap is the hardest part of this backwoods toy to master. First you have to hold the cap so that it is supported on both sides by the index fingers of both your hands. Next, fold your thumbs over to hold the cap in place against your index fingers. Now, and this is where it takes some practice. Bring the base of your thumbs together so that they are snug against each other from the first to the second knuckles. Now, bring the tips of your thumbs away from each other slightly so you can see a V shaped section of the acorn cap. Some people's thumbs naturally take on this position when holding something small, others have to learn how to hold the cap without smashing it to bits.
Once you've mastered the hold, the whistle itself is easy. You place you lower lip firmly against you thumb, just below the knuckles. Purse your upper lip and blow gently into the V shape between your thumbs. If you here a soft whistle that is breathy sounding, then the V shape is to big. If no sound at all comes out then the V shape is to small. Reposition your thumbs and try again. Once you can get the cap to whistle you can alter the volume by blowing harder or softer.
And there you have it. You can now wow your family and friends with this neat little toy, and you just might be able to save your life some day should you ever wander off the beaten path.