How do I add an edge overlay to the edge of an alpha?

well, it was a very frustrating night for me, not near as fun as last night was, lol

I have some ideas what I want to do, but I'm not sure quite sure how to go about it.

I've got the image cut in half vertically on 2 alpha with a threshold slider to make that alpha slide up and down. And then I put the original image back on the top and some bricks on the bottom. So far so good, I've got a neat little waynescoat going on.

But theres 2 important things missing.
1) I need to figure out how to lay a capstone on top of it, eg, a row of bricks with some sort of bevel to give it the appearance of laying at a different angle.
2) I need to get the mortar spacing to line up more evenly with the height of the bricks. ( #1 might solve this just by covering the edge )


Any advice for a confused n00b would be much appreciated.

actually you do it simpler

ohhhh wow, thanks guys, thats way easier than the way I was cutting 2 alphas in half and putting them back together!!

Here is my super lazy method