'Cot Safe' Foam

[mcaddy]

We've been looking to use the Cot Bed as an oversized Co-sleeper, however, we've got a ledge on the side of our bed that'll need covering, it's a 150mm width with 8mm depth. Option 1 is to buy a cheap foam mattress and chop it up, however this seems wasteful as we'll be throwing away 3/4 of the foam. Option 2 would be to buy 'cut to size' but I'm not sure what makes foam 'Cot safe', can anyone advise?

So, whilst looking for foam info, I spotted that Ikea stock a £15 mattress, it's quite thin and probably no good for long term use (as an actual mattress), however it was the ideal for my little project, an afternoon of woodwork and needle work and I have my finished 'gap filler'.

Much the same set up in my bedroom (used for four children now). I roll up a spare single duvet and shove it down the gap.

Not exactly 'cot safe', but works.