Hemming is about the most versatile thing you can do in sewing I believe.
Shorten pants, shorten curtains, even create forts!
(Yes...there should be an "e" at the end of "Jak")
Start with your fabric, whatever it is, and fold one raw edge over about 1/4 of an inch
Fold it over one more time a 1/4 of an inch again.
This hides the raw edge and prevents unraveling.
Sew along the top of the seam.
That's it you're done! Now go shorten some dresses, hem those jeans or make a bunk bed fort! =D