There are so many tools and options to use in Photoshop, it's almost impossible to figure it all out by yourself. Many times I find myself attempting the same task many times, all the while thinking "there has to be a faster way to do this". One thing I finally figured out how to do is create a simple photo mat that's uniformly draw around my photo shape.
Before I would draw a rectangle shape to clip my photo, then draw another rectangle behind that shape that was a little bit bigger to use for clipping a paper for my photo mat. Because I used the custom shape tool for drawing the rectangle, I could never get the sides to be of uniform thickness. I knew there had to be a quicker way to do this but I never managed to sit down and research the right tool to use.
Of course, once you find the right tool, you're kicking yourself for not figuring it out sooner! LOL! So I finally got to use the Image/Free Transform option to make a perfectly uniform mat surrounding my photo.
Here's my layout with a photo that I want to put a mat around. I've drawn a rectangle, loaded my photo, and clipped the photo to the shape layer.
Next you can select the rectangle shape layer and duplicate it. I've renamed the mat layer to "Mat1". Then I turn off (or make invisible) the photo layer and the rectangle photo shape layer.
With your mat layer selected, you click on Image, then Transform, then Free Transform.
You'll then be given a choice for how much you'd like to enlarge your layer (enter in a number in the Width and Height box). I've used anywhere from 105% to 110% for my matting sizes. Make sure you check the Constrain Proportions box so that your layer will be uniformly enlarged.
I colored the mat white. Here's my photo with a perfectly sized mat around it.
Now, wasn't that easy? I just wish I found out how to use that tool sooner!
Have fun putting mats around your photos this week!