[Pebbles82]

I would think a complete circular cork log would be a bit heavier than one that is a semi circle/open underneath, yes, but cork is naturally light. It won't even sink in substrate unless pushed down - and because the area is so spread, it can't really squash a hamster in one area if tunnelled under. Not like a heavy ceramic bowl or a heavy wood house eg. But I take your point if it's a particular large one, that is a full circle rather than half circle, and a dwarf hamster - unless one end is supported on something eg.

I think if a hamster tunneled under it so it went further down, even if the hamster tunneled all the substrate out under it right to the bottom of the cage, they could still get out from under it or push it up a bit!