Drawing details- picking a curved line to draw a hatch outline

[Anonymous]

I have curved underbelly of a massive stair.  In order to draw the the detail, I would like to pick this curved line of the underbelly to make a hatch but unable to.  Is there a way around this or is this just something I have to work around?

[loboarch]

You are probably not able to pick the line because it is not in one plane.  The pick line tool needs the picked element to exist in one plane in order to work.  In this case you will probably have to manually draw an approximate version of the line for the edge of the filled region.

I am not sure of the condition you are trying to represent, but instead of hatching you might want to change to material of the stair so a surface material is applied.  You could also apply a material as paint to a surface if it is just the underside of the stair that needs the pattern.