I used the slidelock on my JT ruler and it still slid. The thing is, the slidelock didn't slide off the JT ruler but even with it, there is still no anti-slip between the JT ruler and the fabric. so what's the point, other than holding it down tighter?
I actually don't like the slidelock as much as others do so that may also be a factor. I can't hold it and cut the entire length without moving my hand because it's not wide enough. My thumb knuckle gets in the way of the cutter. And yes I'm using the wider side.