Robert the tops aren't mortised. That'd probably be something to do. But the top rails are pretty tight on there. When I made them, I didn't glue anything. All joints were just screwed together. So it didn't take long for them to become loose. Just this last year though I took them apart, glued them and screwed them back together. They're a lot stronger now. However, the weakest part is still where the legs attach to the feet. If I made them again I'd come up with something different to do there.
Dave there are holes in the uprights and then a piece of dowel is inserted at the height you want. That's the best feature to me, being able to take your work to different heights!! :wink_smil
Tom