By John Flanagan
Revit Architecture 2015: Editing Elements Interactively - Inserting and Aligning Components
Using the Spacebar
You can use the spacebar to rotate an element, both at the time of initial placement and after it has been placed. In addition to rotating an object in 90-degree increments, pressing the spacebar will locate any nearby non-orthogonal references (walls, grids, or reference planes) as rotation candidates. This is a great time-saving command to become familiar with because you can forgo the necessity of using an additional tool, such as Rotate And Mirror, after placing an object.
The following video illustrates this editing tip.