Hi Bob, which part has the 3 lines that you were trying to make a plane with? Was it this little area here or some other spot? :



But you seem to have a little plane filling in that triangle area already.

Note that if you have some curves or edges that are in one plane and you want to make a surface that goes through them, you can select them and then use the Construct > Planar command to do that, it is located here:



The draw tools like Draw solid > Plane are for drawing a rectangular shaped plane by picking some points - basically all the draw tools work by picking points, the stuff in the Construct tools on the other hand produce some result by selecting objects to work on.

Does that help? If not then I may need some more details.

- Michael