You can split a wall along a horizontal line in an elevation or a 3D view.
After you split a wall, Revit LT treats it as 2 separate walls, which means that you can modify one part independently of the other.
For example, in a 2-level building, suppose you snap the split to Level 2, and the top piece has a base constraint of Level 1. The lower wall has a height constraint of Level 2. If you split the walls at another point away from the levels, the lower wall has an explicit height constraint, while the top wall has a value for the base offset. For more explanation of these properties, see Wall Instance Properties.
A temporary horizontal line displays on the wall when you place the cursor near vertical edges. If desired, you can snap to levels, so you split the wall evenly between levels.
A permanent horizontal line displays on the wall indicating the split.