Doing hibernation for the first time this year, scary

For each tort, we've got a cardboard box (the type used for A4 paper), which fits fairly snuggly inside a lidded polystyrene box, with a very small space between the boxes for a bit of shredded paper.  We know we need to make holes for ventilation - can anyone give us an idea of how many/what size the holes should be and where -  I was thinking just in the lid?

Thank you.

Hi,

I used to put a few holes in the side of the inner box as well as the lid when i used the box method. You need about a dozen holes in the top and about the same size as a pencil (circumference)

Ali

Thanks Ali, will do that. 

Can't bear the filthy looks one of our girls is giving us due to the lack of food!!  Feel bad, but going to be firm.