Cuts an element (such as a wall or line) at a selected point, or removes a segment between 2 points.
Splitting wall with Delete Inner Segment option selected
Wall with removed inner segment
When you split a wall, the resulting parts are individual walls that can be worked on independently.
When you split a pipe, a fitting is added according to the settings in the routing preferences. Revit uses the contents of the Union field. If a Union is not defined, then Revit uses the contents of the Flange field. If both a Union and a Flange are defined, the contents of the Flange field are used. When you split a duct, Revit uses the contents of the Union field.