I thought the same thing, I was disappointed when I first started building the rack but then at the end when it was all together they all slid really smooth with no catching. Maybe I just had to beat on it a lot putting the top levels on LOL. I actually put a small hatchling in an old ARS-70 series tub, I know that tub is way to big for a small baby king snake but it did get out between the top of the tub and the rack, the tub fit pretty loose in there. That won't happen with this rack, the tolerances are spot on, you probably can hardly get a piece of paper in that slot between the tub and the rack. Now the tubs slide in as smooth as glass.