patricej

that's because he had the ruler wrong side up when he was trimming the fabric stack to get his first straight line.
i did notice that the ruler slipped just a wee little bit when he cut the first strip, but many brands will do that if you aren't super careful.

it's an interesting design and the prices are within the same range as most brands.

i don't see why it wouldn't work with a martelli cutter.

i noticed he was left-handed, so this is the first ruler i've seen that appears to be either deliberately or accidentally designed for lefties.

if you need to cut several layers it looks like a less expensive, and more accurate, alternative to the big clunky strip cutting tools out there. definitely less expensive than a cutting machine.

i'm not sure it would be useful if you were cutting just one or a very few layers of fabric, though. that guide bar might become more of a nuisance than an aide. would the measurements be thrown off because the ruler doesn't lay flat? possible, i think.