I have the Micro Mark corner punch and it worked very well. I've only used it for one structure, since I'm not much of a scratchbuilder. I was concerned as well as to how long it would stay sharp, but was as sharp at the end (probably 15 or so windows/doors) as the beginning. Not having a drill press at the time, I gently tapped it with a small hammer to cut the corners out over a mat.
Jeff






