This is something I worked up on a thread over in the Acad2013etc Forum, but since neither the request nor the resulting routine are version-specific (and, if I do say so myself, I think it's pretty cool), I thought I'd post it here, so anyone Searching for such a thing who looks only in the Customization Forum will be able to find it.
It's ConstLines.lsp with its RX command [= Rays/Xlines combined -- I would have used XR if it weren't already the default alias for Xref].
In one running of the command, you can draw as many Construction Lines in the form of Rays and/or Xlines as you want, switch between the two, choose preset options for all possible orthogonal directions for either, plus options for a "Free" direction [User picks second point for direction of each one] or an "Angle" option [User specifies a particular angle that becomes the default]. It remembers all choices, independently for Rays and for Xlines, and offers them as defaults on subsequent use. You can Undo one at a time within the command, e.g. if one lands in the wrong place or at the wrong angle or something, and keep going, or Undo the entire command afterwards. It makes its own non-plotting Layer to draw them on [see instructions to change the name and properties as you prefer].
See full commentary at the top of the file, and some within it.
