Thanks everyone for putting time into helping me ...
> My current workaround is to duplicate the tab first
Good suggestion. Doing that now.
> reassembled (badly)
Yes. At the time I created that object I was either drunk (kidding), or in a rush. It is an example of rapidly hacking and hewing until I got something that looked good at a high altitude. I should point out that while this is for production, it uses desktop 3d printing and any feature smaller that 0.1 mm can be ignored. I have daydreamed of witing a F360 extension that just dissolves all features smaller than a threshold. Errors pointed out above would disappear. I am mostly a software programmer which probably explains my bad designs.
> hold the left mouse button down
Aha. Very useful. I have now been able to accomplish the original extruding task. Between projects I should take a week off and go through *all* the tutorials.
> what operation is it you where wanting to perform on the edge of that part?
So now we start the third topic of this thread. I am trying to "shrink" the edge of the object to compensate for filament expanding sideways. The mating hole for this part has already been produced and this part is too large. I can't use scaling since I need a fixed distance (0.2 mm) on all parts of the edge. My approach was to sweep a rectangle around the edge and subtract the resulting body from the part. I ran into a brick wall when the swept body was too damaged to be used. This is the Body1501 I referred to earlier. Now I should be able to use the spline-copied edge for sweeping.
Dare I hope that there is some simple way to shrink an edge that I have missed? Offset-face was an obvious candidate that didn't work for me.
