Make a really good whistle from an acorn cup

This time of year, if you asked me to empty my pockets, you’d find an acorn cup.



Did you know they make excellent and very loud whistles.

Hold it between your index fingers thumbs to create a small triangular opening like this



And then blow . . . The harder, the louder. Also works for beer bottles, pen lids . . .

If I ever do my own PEX, this will be a necessary badge bit.