They use a metallic looking ruler for measuring centering apparently. There was a photo they posted to their instagram showing it that they later deleted after some backlash.
Here is a thread that popped up when that insta photo came about.
The whole “no gloves” thing I have no issue with, but I personally wouldn’t ever touch the cards with anything but my bare clean hands and a penny sleeve/card saver. Every time I see an opening video with gloves I cringe a little, but I guess it may be better than bare hands holding a ruler against the card…