Sometimes when i edit a wall and do the push/pull (copy) command, one of the surfaces, especially if I’m connected to another wall, disappears.
How come? If I add a line on the “ghost” surface, it reappears,
Are you using groups and components? Have you assigned tags to raw geometry (edges, faces)?
It also relies on factors like the orientation of the face and the direction you are PushPulling it relative to its normal. There’s a toggle key-press [Ctrl?] in PushPull - using this will delete/keep the original face when you extrude it, depending on those factors…
Thanks - no - after 5 years on SketchUp, I still haven’t done tags… The surfaces are not grouped, in this case -
Yup - thanks - I did toggle but, every once in a while, a surface just disappears.
You can continue working as you are now and face a lot of errors and such, or you can take a course on the basics of SketchUp and learn to work correctly.
Learn about groups, components and tags and you will make your work much easier.
Make each element of the construction a group/component, just as it is in reality.
SketchUp YouTube - SquareOne
SketchUp Campus - courses
oh, i do groups and components - the tags are just what we called layers in AutoCad, when i first started using CAD back in 1984. I find that, instead of tags, I set up groups that I can click off and on easily for my various drawings and renderings.
Thanks, though!
And when you have groups and components, do you still lose faces when using PushPull?
Anyway, do what you think is best for you.
Also take into account the explanation provided by TIG, it is very useful.
yeah - it’s weird. I must have random point or something that these click onto - It happens infrequently but, I like to get better every day with my drafting, even though I’ve been doing if since 1984! 
Thanks again - all the best!
Next time you have a face that “disappears”, save out that file and post it here so we can diagnose. There are many factors that might cause this apparent behavior and it’s next to impossible to guess which kind of mistake is being made without watching over your shoulder while you model, but looking at one of your models can give us lots of clues.
I do wonder exactly what you mean by:
There is the push/pull tool, and push/pull with add face modifier key, and there is the move tool with the copy modifier key, and there is copy/paste… But there is no push/pull copy.
Perhaps unpacking what you mean by this term might shed some light on why this is happening to you?
You mean the original face you start pushing or pulling disappears? That does happen when there are other lines and faces connected to it, and SU can’t tell whether you’re trying to turn a 2D face into a 3D solid, or whether you’re just manipulating a face by adding some depth. As others said, if SU gets it wrong, you just use the modifier key to get the other.
So sorry that I left the chat last week - yes, I do mean the push/pull with face add modifier key. It’s a constant source of frustration, but I’m pretty sure that it’s what RTCool mentioned. I draw a plane and then push/pull modify to create walls but, if I go back to edit an adjoining wall, that’s where this issue shows up on occasion. I started using “CAD” back in 1984 when we had to be REALLY diligent about erasing extraneous line and I’m sure that some of my old habits are messing things up. I do love SketchUp, though. I also have a subscription to Chief Architect but haven’t used it in a year or so because I find it’s hard to be creative with it. Nice folks, though, over there and I don’t have this problem with that spftware.