You can reserve hostel beds at larger "official" Hosteling International hostels anywhere in the world. The only complaint I have is that at many hostels you can only reserve a dorm bed, even if the hostel offers private rooms. And some smaller or more remote hostels don't reserve on this site, though usually they are listed. Generally, the site works OK. Something many people don't know is that the Hosteling International hostels are not really "youth" hostels. Us older folks can stay there, too. I can no longer manage an upper bunk. I have had good luck e-mailing the hostel and asking them to give me a lower.