My problem is that I was given the attached file to modify. It is a thread adapter, so I need to change the threading on both ends (diameter, pitch, ...). It was modeled as a surface so my first thought was to turn it into a part (in a previous post someone helped me achieve this). I became interested in surfacing, so I completed some tutorials. However, things are straight forward when starting from scratch, but with the file attached I am not sure how to modify it, for example, trying to extend a face gives me the error "There is no extend boundary", for which Google has no answer. Any hints would be much appreciated!