I normally use rhino for other purposes, but recently I am designing a house. I am extruding surfaces but constantly need to change the size of shapes as I design further. This process leaves lines on the surfaces (when I extrude the surface from the end of the previous one or make them smaller. I know I can start over from the curves, but
I am wondering if there is a way to delete the lines left from the previous smaller or larger shapes like in sketchup. Is there a push/pull option? I have attached an image of my issue
Have a look at the MergeSrf and MergeAllFaces commands.
EPIC! Thanks John works like a charm!
Thanks. I was struggling with that today. Your advice came right on time.
Also, remeber that you can modify a polysurface simply sub-selecting their faces or the edges and moving them.
Something like the solid editing but quicker.
Ciao.
Thanks @lucio_zadra. Your method would be perfect, but I am running parallels and I think my commands are different. I have attempted to use command+shift+LMB to no avail. CTRL+Shift+LMB doesnt seem to work 
brobe,
the command SolidPtOn might be a good tool for you also. I love it so much I have it on my f9 key.