I think I now understand just enough of how router bits work, but I'd like to confirm I got it right.
I will use a router to round the edges of shelves. The thickness of the plywood is 3/4". Initially I was hoping to get a perfect half-circle and use 3/8" round-over carbide bits. But now I gathered that when doing the first side I'll be able to rest the router bit on the edge just fine, but after turning each piece over to work on the other side, there will no longer be anything to rest on. I'd then need something a lot more elaborate for my spartan beginner set, to be able to finish the second side, and so the top part of the illustration is not doable.
Instead, I'm gathering I can only aim for the less attractive 1/4" round-over on each side. as illustrated in the bottom part of the illustration.
Did I get it right? Does it sound to you like I understand what I'll be doing?
The profile I'll be working on looks partly as shown below.