I'm using AutoCAD 2015. I am new to this forum. This is my first post. Whe I extrude a already extruded solid, a line appears. Can anybody help me to get rid of this line or to avoid it happening. It is part of the solid. Isoline=0 does not work. Thank you.

You extruded a solid then extruded it a second time?  I did not know that was possible.  What visual style are you working in?  2Dwireframe or 3Dhidden?  Could that line be a piece of 2D geometry?

Hi John,I produced a solid. Days later I realized it was too short. Then I
extruded (lengthened it). Came up with this unerasable line or isoline in the
lengthened part. This never happened with previous versions. Only now with
2015. I’m working in 2D wireframe.

Without a copy of the drawing I can't say for sure what the origin of the line might be.  Could be an anomaly in your 3D model.
John Connor2015-04-05 18:37:27

Hi John,Here is the file, please see what you can make of it.Thank you.uploads/549558/Line.dwg