Hi Maxim,

Thanks as usual for your kind support. I don't know why the other two objects are only surfaces but not solid. I used the same method to plot these three objects. Draw four lines to form a square, extrude to the third dimension, then subtract unnecessary region. (Maybe I forgot to Join the four lines before Extrude? I guess not likely for this mistake)

I never used the Explode command, so do not have any Original object.

Is there any easy way to form a solid object from these surfaces in my uploaded file? I do not wanna waste time plotting again...