Does a bedside cot work with a 'framed' bed or are they only any good with a divan?

[MrsKitty]

Loving the idea of a bedside cot for DC2 (due Oct) but am wondering if it'll work with a framed bed? How can I prevent a matress gap / baby getting wedged in the gap?

Thanks

We have the Mothercare bedside cot.
We push the mattress right against ours and stuff blankets at the far away side.

We just took the side off our regular cot - worked fine . Cots usually have adjustable bases so you can get it to a height to match your bed. When we slid the cot mattress up to fit snugly against our mattress there was a gap on the other side, but we just rolled up a fleece blanket and stuffed it in there. Worked a treat!