When is a Car "Level" - Home Front End Alignment

Well I wasn't expecting this kind of response! Many thanks for those of you who commented.

I need to get it in the ballpark after a total front end rebuild. Once its close I can get to a more optimal place to do the work perfectly.

This isn't my first home alignment I've done, I just usually have the benefit of being in my garage which has a remarkable level floor. Using the simple Longacre racing stuff I have yet to have a problem.