--Metallic marker (I like Prismacolor and buy them on sale at HL)
--Raised ruler (mine has a felt backing; a raised ruler won't wick ink underneath and make a mess)
Start by placing your stamped panel on scrap paper. Align the ruler along one edge, leaving a little less than 1/8th inch of the panel showing.
Prime the marker on the scrap paper to make sure the ink is flowing well. Then, starting on one corner, run the pen smoothly and quickly across the edge. Check to make sure the pen laid the ink down smoothly. If not, run the pen over the edge a second time before moving the ruler.
Once you have a satisfactory line, carefully lift the ruler WITHOUT LETTING the inked edge touch your stamped panel. Wait a few seconds for the ink on the paper to dry. Rotate the panel, and repeat the edging for all sides.
If you've notched the corners of your panel, as I have here, you can edge the corners free-hand with the marker once the straight edges are finished.
Here's the finished card, a 4.25-inch square using PTI's Stocking Prints and Signature Christmas. I really wanted to do this layout as a one-layer card, but it just didn't look right. I figured this would be a good card for the tutorial, so I went for it. I cut it out as a 3x3 panel, edged it, and made the smaller, square card. It was a quick and easy way to make a relatively flat, very simple card a bit special.
I hope these pictures clarify the technique because with just a bit of practice and some very inexpensive supplies, it's a super-easy way to kick CAS cards up a notch.
stamps: PTI Stocking Prints, Signature Christmas
cardstock: PTI vintage cream
ink: Brilliance Pearlescent Ivy, Palette Noir
accessories: ruler, metallic marker, dimensionals, ticket corner punch