How do I get rid of it?

sorry for all the questions, you are all a great help! i got the shape filled but now when I try to paint it, it wont fill with the material. Strangely when I go to undo, it says I have have applied the paint and can hence undo it, but I cant see the material...I don't think this problem is limited to the shape I just made.

I am trying to make a plane that is essentially a rectangle with a curve drawn through it connecting two of the parallel sides. I first create a rectangular plane and then draw the curve connecting the two sides using the downloaded Bezier curve tool but then when I try to select the portion of the plane that I want to delete, it just selects the whole plane. How can I divide the plane with a curve?

So I have color by axis turned on.I am attempting to draw a certain long line parallel to the red axis. It illuminates red as I extend it and when the endpoint snaps but as soon as I click to establish the line, it turns black...why?

thanks for all the help! I think a found a way that suits my needs. I used Bezier curves to connect two perpendicular intersecting rectangles and then used curve-stitcher to create the strip. Pretty quick, if not perfectly accurate

How would I go about making a simple rectangular strip that twists one time so that each end is in the same position, but one end has been rotated 180 degrees? I'm assuming I'll have to use the bezier curve plugin?

oh but that color by axis does help. Thank you!
maybe i misinterpreted what you were saying
i think i understand now

I understand that my model is not square, the plank-like floor that the stairs rise from is not a rectangle but an elongated trapezoid. This is intentional. In other words, I had to create the stairs using the line tool because the stairs are not rectangles. Shouldn't I be able to fill faces that don't line up with axes??

sure, there are numerous places where I am having this problem. Having not really used sketchup before this model, I am not really acquainted with grouping and I think this is at the root of my problems. As you can see I am having trouble filling the sides of the staircase closest to the (currently) open street facade and the bottom of the 3 angled stairs on the young adults raised runner.Library Site.skp

Could somebody just list the possible reasons why I might not be able to fill a face? I have retraced its outline to ensure closure, but it will not fill. This a recurrent problem that is bugging me.