Thanks for all the advise. Following it solved 2 of my three face problems. I see that this is a common difficulty. Using the midpoints approach on the third problem resulted in conflicting feedback about where the error might be. Using different colors for lines in different axes was helpful but the color of a SELECTED line is the same as the color of the vertical axis; is there a way to change the color for indicating that a line has been selected? The scripts recommended look very useful but I'm out of my element with those. 'Need to do more research before I'll be able to follow that suggestion (unless anyone feels like walking me through an installation). As suggested, I've attached the .skp file for troubleshooting. Thanks again,

Kurt

case.skp

I thought that whenever you enclosed a space with lines that it formed a face. I've got three instances of what should be faces (walls) on a project, but they are invisible (or not there). I have inspected all the intersections carefully and now I'm stuck. Thanks in advance.

Kurt