Can't join open polysurfaces please help

Good afternoon to everyone! I am a Rhino newbie, and I am trying to join 3 open polysurface rings into one ring (it’s a spare part that I want to 3d print for a drawer). I basically created 3 separate extrusions for my ring, the bottom and top ring are identical and the middle ring is thinner and has a protrusion towards the inner part. I opened up the surfaces where I want all rings to attach to each other (hence I made them purposefully open polysurfaces, but for some reason the join doesn’t work between them.

Thank you in advance for your help!
ring.3dm (127.1 KB)

Hello - you’ll need to make sure the pieces touch exactly:

before you can do anything resembling joining. If these did touch exacty (please see Help on object snaps, ‘Osnaps’) or overalp, then in this case a BooleanUnion would do it. But for this, if I understand the goal it is probably easiest to draw the cross section as a polyline and Revolve that.



Thank you so much Pascal, revolving it makes so much more sense actually. I am going to try it now and let you know how it goes.

Again, thank you!