Mostly quote: "If the box is easily slid on the shelf and the snake is in the tub pushing backwards against the ceiling (as they may do when pushing against every surface to see what will give) that will push the box out of the shelf in the same way you do when opening it."
Serpwidgets, does that mean that double acting toggle latches, front and center of the tub between each layer, are a good idea in case those sneaky slitherers figure out how to move the tubs? Or does it mean make 'em tight fitting. (Friction fitting?)
I really appreciate the time you have taken to post these types of projects. I have tools that feel abandoned in the garage and this type of post is on track for me.
Yeah, it means make them so they have some friction to overcome to pull them out. It doesn't have to be ridiculous or anything, just not so loose that it slides effortlessly.