Introduction
Remember the fairytale of Jack and the Beanstalk? The plant which curled into 3 strings like braided hair? Well that's almost what we're gonna make right now... only a little different. This technique is also very cool to do in Photoshop. It can be used for rope, tentacles, hair, silly effects and of course things like a beanstalk or other vines/plants.

Shear
When you open your document and have chosen a background of your liking, create a new layer and use your Rectangular Marquee-Tool to select a long and thin rectangular shape in the middle of your document. Make sure your shape, like mine, is as large as the document itself. With the selection in place, use the PaintBucket to fill it with Black.

While holding SHIFT and ALT, click and drag the bar to the left and you will make an exact duplicate. The ALT will copy your layer and SHIFT will make sure you keep it horizontally aligned. Press CTRL+U and move the bottom slider a little to the right to make it a little lighter so you can spot a difference between them.

Select your first layer again and go to Filter>Distort>Shear and a window will pop up. When you look at the window, there's a small area with a grid and a line vertically with 2 anchorpoints. By clicking on the anchorpoints, you can drag them in a desired shape. if you click on the line or on the grid, you can also add new anchorpoints. Try to add 4 more anchorpoints and make a curvey line like mine below. If you fail because it's a bit tricky, simply press CANCEL and try again!

Once you're pleased, press OK and you will notice your once so straight rectangle is now a curvey line. Remember the Grey copy we made earlier? Press CTRL+F on that layer and notice how it will be Sheared like the other bar. You can obviously also make a copy AFTER you Sheared. It doesn't really matter.

Braiding
Select the Grey layer and press CTRL+T and right click inside the transformation and choose Flip Horizontal from the popup-menu. Now position your Grey layer underneath the Black layer. Now, hold CTRL and click on the thumbnail of the Grey layer to select the layer. Now, select the Black layer. If you would press DELETE now, you would delete all the Black parts that "touch" the Grey parts. We don't want that, since we want it braided. Braiding is where you go over one line and under the next, so that's what we're gonna do.
Grab your Rectangular Marquee-Tool and while holding ALT, remove by deselecting the 1st overlay, the 3rd and the 5th. Why not the 2nd and 4th? Because it's braiding. It's very simple. Use your Marquee-Tool to remove an area from the selection. By doing so, remove the selection over the first overlay, then the 3rd and then the 5th. And keep skipping one if you have more overlays.

By making a new layer above the Grey layer and masking it with the Grey layer by pressing CTRL+SHIFT+G, grab a soft brush and set it to Black and draw some shading on the placed where the Black layer overlaps the Grey layer. Lower the opacity if needed.

If you use more curves and more twists, it's a little harder, but just remember when you start erasing parts of the selection that you keep skipping one. So always go 1-3-5-7-9-11 or 2-4-6-8-10. Also note that I 'd really recommend making the bars both 2 different colors, otherwise you can get confused really fast.

Conclusion
The same technique of overlapping 2 objects, deleting parts and shading certain area's to make it look like the two layers are 3d, can be applied to a lot of other different situations. And as I said, the same thing can be done with hair or plants as well. Just make sure to alter the shading to the thing you're making. Make sure it looks realistic if is has to look realistic and use a hard cell-shading if you're going for a comic-look. Thanks for reading and have fun!