A slip stitch (otherwise known as a ladder stitch) is a very handy stitch to have in your arsenal. It's good for everything from clothing repair to stuffy surgery to being the perfect invisible stitch to close up your newest project. Are you ready to learn this awesome new skill? Let's go!
Today I'm going to teach you a slip stitch based on closing up a seam in a garment. So... you're going to start with a partially open seam, a needle, matching thread, and possibly an iron.
If you haven't already, press or finger-press the entire seam as if it were sewn. That will give you a nice crease to help keep your stitching straight. Then get your needle threaded and we're ready to stitch! I always double up my thread for a little added durability, but it isn't strictly necessary.
To begin your first stitch, you're going to push your needle through the fabric from the wrong side (inside) to the right side (outside). Make sure you're coming out on the seam slightly before where you stopped stitching. This will ensure your entire seam will be closed.
Once you end knot is pulled all the way in against the fabric, you're going to take the needle and insert it directly across from where the thread exited on the other side, again right on that crease. And bring it back out again approximately 1/8" from the entry point, as pictured above.
Continue doing this going back and forth along the length of the opening you need to close. As you can see above, you'll end up with a series of parallel stitches reminiscent of a ladder, which is why some people call it a ladder stitch.
If you look from the inside, you should see a straight line of stitching (hopefully relatively even) traveling the length of what used to be an opening of your seam. Make sure you finish your line of stitching with the thread on the inside of the garment. Now is when the magic happens... Pull the thread tight (not too tight or your seam will pucker) and...
You have a closed hand-stitched seam with no visible stitches! Tie your finishing knot on the inside and you're all done! Like I said earlier, once you master this stitch you'll find it extremely useful in a wide range of circumstances! Practice, practice, practice! You'll be a pro at it in no time!