Join polysurfaces

this is a basic question regarding joining poly surfaces, could you please explain why this object cannot be joined into one poly-surface. thank you
join.3dm (398.3 KB)

because you are trying to join 3 edges at once creating a nonmanifold object wich is not good.

thank you for you reply, any suggestions to create the same shape without having to join 3 edges?


As @DiegoKrause said you have nonmanifold object and if you move & try to join you will get these issues.


what’s the objetive? you can group those objects if you want to move them together

hmm, wouldn’t that be a problem in case of 3D printing?

yes but having only that is not clear what you want or why you need that geometry in that way

so the shape is needed to hold a piece between two surfaces, as shown in the sketch.

then give it some thickness

Thank you