I've just read on a BDC article about the importance of availability that there is a ‘Room decided at check-in’ option. To quote form the article,
"And if you want to keep it flexible, you could even go with a ‘Room decided at check-in’ option, so you can sell all left-over rooms within one room type – and hold back your more expensive rooms until the very last minute!
Here's the BDC article from the 'Knowledge Base'
Does anyone know how to access and implement this option? I have found nothing on the extranet.