Posted 31 July 2012 - 05:23 PM
Okay, I think you are trying to create a frame around an empty spot. You want the empty spot to be transparent. I was able to do this, first in FILE open NEW, next in IMAGE select BACKGROUND COLOR TO TRANSPARENT, next select the square tool, then set the color of the square tool to transparent using the color tool on the right side of the skitch screen, in the sub window choose CUSTOM, then slide the bottom opacity slider all the way to the left to create a transparent color. This is now your color(transparent), next make a square in the skitch pane, it will seem to do nothing since it is transparent, but it is there(if you don't believe it choose the top arrow/4arrows tool and move it over where you made your square and you will see it). Outside of that box, using the color fill tool, with a new color of your choice, fill the outside of the box. You should now see an empty box on the inside with color on the outside. This creates a solid color frame.
It sounds like instead of that, you may have wanted to create a frame showing the image you captured with a transparent spot in the middle. If that is the case I would suggest copying the image into some other image processing program that has png and erasing out the center and then bringing that image into skitch. Skitch Does not allow for changes to occur to the image captured except to place other drawings or text on top of it. That has to be done in another program.