Using the following method, you can edit the shape, or tweak the curves, and it will be automatically reflected on the other side.
Using a guide, draw one half of the shape with the Pen Tool.
Open the Appearance panel
Add a Transform Effect with the following settings:
Edit the curves, and the shape will be automatically reflected.
I'd like to note two things. First, you want to watch your width when you're dealing with shapes. Something that tapers and swells smoothly and consistently will look a lot better.
Also, I find when I'm trying to draw smooth curves that I draw them better if I set the curve handles in a way that they flow from one into the next. Let me illustrate with a ...
You could simply use the Spiral Tool.....
when drawing with the Spiral Tool, tapping the up and down arrows on the keyboard will increase/decrease the amount of arcs as you drag, and holding down the Command/Ctrl key while you drag will allow you to adjust how tight the spiral is.
Then use the Width Tool to add some dimension to the path:
In the end the ...
If you only care about the outside corners, you could use the round corner in stroke settings.
This one is in Illustrator:
And this one is in Photoshop:
Like I said though, this will only make the outer corners round. The inner corners will still be sharp. The round corners stylize effect in illustrator is more versatile and controllable.
There are actually many ways to accomplish rounded shapes....
You can draw circles at ends of rectangles and use Pathfinder or the Shape Builder Tool.
You can use Effect > Stylize > Round Corners
You can use VectorScribe from Astute Graphics (third party $$ plug in -- See note below).
You can use thick strokes with round end caps.
And then, of course, ...
Update: For Photoshop CC
This is now possible in Photoshop CC by drawing your path and adjusting the Stroke options in the Control bar across the top of the screen.
Previous answer (CS6 or earlier)
Create a closed shape with the Pen Tool.
Add your vector stroke to it.
Add a layer Mask (raster or vector) to your vector layer and mask away the section of ...
There's a trick... it's not an open path. It's a closed path with 3 sides outside the canvas.
By making 3 sides fall off the canvas, their edges aren't seen, the path is closed and you can then apply layer styles to it.
If you are trying to save the shape for further manipulation, all you need to do is name the path in the Path window so it won't get overwritten when you create another shape.
If you don't see your Paths window go to Window > Path to show it.
To create a shape with the pen tool from the start, make sure the Shape Layer icon is selected.
Easiest method I use...
click for the second anchor away from the other path, while holding the click depress the Space bar and drag the click where you want it to be.
This will prevent the two paths from joining. You just have to click and move with the spacebar down. This is generally the fastest method since you don't need to lock or hide or isolate ...
As per request, a script to do this on selected paths. This is an alternative for @CConroy answer that may make things easier to do in the long run. It draws symbols on points and tangents and connects the tangents with lines, You can use symbols palette to change how they look after the fact. Might be useful for somebody.
Put following in a .jsx file and ...
Draw your path and merely set the stroke options in the Control Bar across the top of the screen. This is possible in CS6 or newer with vector layers.
For versions prior to Photoshop CS6 you'll need to check here: Do paths in Adobe Photoshop have to be closed?
Update CC 2018 (CC v.19) release
As of the latest version of Photoshop CC update there is now built-in smoothing on brush tools. On your main toolbar there's a Smoothing section and in your Brush settings is a new Smoothing option as well.
Lazy Nezumi Pro - 32€
Lazy Nezumi Pro is a Windows app that helps you draw smooth, beautiful lines, with your mouse ...
If the path is a stroke
Make a square that cuts off the top part of the V shape. You do not need a fill or stroke for the square. Select both, go to Object -> Clipping Mask -> Make.
If the path is expanded
You can use the direct select tool and manually move the inner-endpoints down.
Make a square that cuts off the top part of the V shape.
Open the ...
It would be far easier to draw in Illustrator and then copy paste into Photoshop. More on this later.
How to do this in Photoshop
Unfortunately theres no direct way of doing this in Photoshop. Don't let that discourage you it is still possible to this. We just need to fish slightly further.
Draw a line on horizontal or vertical.
Select the line.
Photoshop has had the ability to save paths in JPGs for a while. (CS5.5 I think, might have been CS6)
As long as you don't use Save for Web and use Save As for JPG, they'll be there if the jpg is subsequently opened in Photoshop.
Other software may not see the paths.
It's similar to how Fireworks used to save PNGs with layers... it's all proprietary data ...
A similar approach can be taken in Photoshop, but here is one solution done in Illustrator:
1) Draw rectangle
2) Select rectangle > Effect > Stylize > Rounded Corners > ~10px
3) Select Direction Arrow (a) > Grab top right corner of rectangle holding shift
to keep structure and create your desired angle
4) Select rectangle > Object > ...
Let's say we have 2 shapes as on your picture (face + head).
I make these two shapes overlapping with the face layer below the "head":
I duplicate the head layer, Select 1 head and face layers and by Pathfinder operation Minus Back get this perfect match -
Let's say you should create long ray as you asked.
I choose on Direct Selection Tool (A) ...
Start by drawing a line and circle and style each how you would like the polygon sides and vertices to look.
Drag the line to the Brushes panel and choose Pattern Brush. In the Pattern Brush Options dialog, set the first tile (Outer Corner) to None and hit OK.
Then, Option-drag your circle onto the Brushes Panel into that first tile slot. You'll return to ...
There's no such setting. Illustrator simply does not function that way. You may be accustomed to Photoshop creating new layers for everything. Those are necessary in Photoshop. They aren't needed in Illustrator.
The only time Illustrator creates a new Layer is when the user tells it to. In other words, if you want a new layer you have to manually create it.
The pen tool forms a path. It looks like you have a dark blue fill in your stroke and fill settings. Change the fill to "no fill" and you should just see the paths (with whatever stroke you have set). Any open path (which is not a closed shape) will fill even without being closed.
If you have Adobe Illustrator and all you need are rectangles, you can simply use a dashed stroke with a large stroke weight....
If you need one rectangle, as AndroidHustle suggests, simply untick the "Dashed Line" option.
Then to edit the rectangles, choose Object > Expand. Then copy this in Illustrator, switch to Photoshop and Paste as a Shape Layer.
Smart guides (ctrl-u / cmd-u) can help, but they aren't always enough, especially on curves.
Often it's best to overlapping path lines - if it's solid fill it might be better to just go underneath, and if it's empty outlines it might be better to just stop when you connect the line (like you would if drawing on paper: you wouldn't carefully draw over the ...
Sorry this is well past any usefulness to the original poster most likely. I realize this is a very old question. However, this may be helpful to others. This has been a solution in Illustrator since practically it's inception and still works today (CC2018 the most recent version as of this writing).
Hold down the Option/Alt key with the Pen Tool active ...
You can use the scale tool with the tangent. Once the tangent is selected with the direct selection tool (a) click on the vertex tangent to move scale pivot to vertex. By holding Shift you can now constrain the scaling to be equal in both direction, which achieves what you want. You can also scale both tangents in unison this way.
Screencast 1: Moving ...