I have 3 C-Serpents racks and they are quite tight fitting so there is not enough gap for even a hatchling to escape out of a gap between the tub and shelf.
I have however had a few larger bp's... 850g Pinstripe and a 825g Pastel wedge their tubs out far enough to nearly escape. They are in V18 tubs and have enough strength to be able to use their mass to wedge the tub out of the shelf a bit. First time I thought I didn't push the tub in all the way after cleaning... second time there was no mistaking my Pin wedged her tub out. Thankfully they were never able to wedge the tub out enough to escape.
Here is my fix..... I used galvanized roofing nails with the tip ground smooth and my dremel to make a hole for the nail to fit into. The heads are so flat that they do not cause interference when removing a tub from the shelf.
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