We've probably all had an evil pair of jeans before. You know the type. The one that seems so innocent, and yet is actively devising a wicked plan to embarrass its wearer.
There is a tiny, spring-activated lock in the zipper slider itself that is supposed to keep the slider in place. A tiny hook comes down and lodges in between the zipper teeth, rendering the slider immobile. When you raise the little pull tab, the hook retracts, enabling you to move the slider up and down. You can see the hook working properly in my first two pictures.
Jeans zippers can fail when the tiny hook snaps off, or if the spring mechanism breaks and leaves the slider with nothing to hold it up. Fortunately, it's quite easy to fix it yourself. Here's how!
You will need a discarded pair of jeans from which you can take a working zipper slider. You will also need basic sewing supplies.
Step 1: Take a Replacement Slider From an Old Pair of Jeans
Get an old pair of jeans that you don't want anymore. (Be sure that it has a zipper slider that works properly!)
Cut through both sides of the zipper tape, and pull the slider right off.
Step 2: Remove the Broken Slider
Now grab the pair of jeans with the broken zipper slider. Using a seam ripper, cut through the waistband stitches that trap the top of the zipper tape inside the waistband. You don't need to cut any stitches other than the waistband stitches! Leave the stitches that are going alongside the zipper teeth right where they are.
Now pull the top ends of the zipper tape out of the waistband.
Grab the broken zipper slider, and zip it right off the top of the zipper. Leave the two sides of the zipper together just the way they are, and throw away the broken slider.
Step 3: Add the New Slider
Take the working slider and carefully feed the top of the zipper tape through the bottom of the slider. Push the slider down until you get to the zipper teeth.
Remember that hook that's supposed to hold the slider up? It won't let the zipper slider come down onto the zipper teeth unless you lift the pull tab up! So make sure you raise the pull tab, and move the zipper slider down onto the zipper teeth.
Step 4: Sew It Up!
Now tuck the top of the zipper tape back into the waistband, where it was.
Use a jeans needle (Size 16, or size 100 if you're from Europe), or a hand needle and thimble if you don't want to use a sewing machine. Sew on the original stitching line, starting a half inch or so before the stitches that you cut, and ending a half inch or so past the cut stitches. Backstitch at the beginning and end to lock your stitches.
I'm using pink thread so that it would be easy for you to see, but of course you would want to use a matching blue thread.
And now you're done! Rock those pants, secure in the knowledge that you have thwarted their evil plan to embarrass you! :D