Planning is accelerated by copying elements from an existing floor to another floor. This can be useful e.g. when creating main walls on several floors, as their floor plan is mostly the same at different levels.
The floors of ARCHLine.XP are a logical unit, not a physical boundary. So the element placed on the floor belongs to the floor, but its geometry is not affected by the properties of the floor (floor height and height). This means that an element placed on a floor does not have to be physically within the lower and upper limit of the floor, it can “protrude from there”. This is also required, for example, in level-shifting buildings.