A recurring theme is the use of model lines to indicate where an opening occurs in a floor. In the transition from 2D drafting it seems a bit counterintuitive to bother to create a floor. In plans the perimeter of the building defines the floor...or does it? Sometimes. In Revit the task of creating a floor should essentially equal the task of developing a slab edge plan, at least the sketching of it.
When it comes to predictable poorly coordinated work we need look no further than shaft floor penetrations (hmmm, we should look further, but not for this post). Thus the subject of the post. Remember to use the Shaft Opening tool in Revit instead of sketching Lines, be they Detail or Model.
Two features stand out for Shaft Openings, they cut through floors, ceilings and roofs they come into contact with and they can include Symbolic linework to represent the classic "X" for an opening, the "yin/yang" of vertical round duct risers or elevator car graphics for example.
You find the tool via Modelling (Design Bar or Menu) > Opening > Shaft Opening. They are sketch based elements, meaning you define them in Sketch Mode.
When you are done you must "Finish Sketch" to finish. To change them you must select them and then choose "Edit" from the Options Bar. A Shaft Opening sketch can include multiple closed boundaries, to describe multiple openings, but they will all rise or fall exactly the same way, according to their Base and Top Constraint parameters as well as Base and Top Offset parameters. This means you must use separate Shaft Openings when their shape/profile changes at different elevations.
You can refer to THIS post and THAT post for additional comments.
Don't forget your friend, the Shaft Opening tool.