Frank is right as a beginner to be confused. Here in the UK the most popular hive is the National which has bottom bee space instead of top as Frank describes. However many people recognise that top is more efficient and modify their hives or, if they build their own, make them with top space. They also buy second hand equipment which, of course doesn't quite match their own. Inevitably the equipment gets mixed with predictable results. I once inherited an apiary of home made CDB hives (an obsolete Irish design). The chap who made them was a craftsman. Everything fitted. Nothing was stuck with propolis or burr comb. They were and are a joy to work with and the bees love them. Chris