i need to snap to an existing line but I can't - but can sometimes

[GR-Designs]

When I go to cross section mode to adjust my stepped concrete wall, sometimes I can get a cad line to snap to an existing feature and sometimes I can't --- why? why not always snap to an existing feature all the time?

[GR-Designs]

if it helps: I just discovered it makes a difference if you take a section from outside the building (which yields no snap options) and a section from inside (which yields snaps to the concrete foundation which is what I wanted) ---

[Allen Brown]

Often, I will have to draw a short cad line over an existing line in elevation view to snap to it. Not ideal, but not a big deal.