Are you talking about rotating a detail/section mark, after it has been placed, so that it's perpendicular to a wall? If so, the answer is: you can't. At least, not with any degree of accuracy. Sure, you can get it close, but you'll still probably run into problems when trying to dimension to certain items. You're going to have to re-create the section/detail mark and make sure that the marker snaps where you want it when creating the callout.