A railing can be just a handrail, or a balustrade with posts, top/bottom rails and newels. Using the Railing on Stair Center tool you can insert a railing along the center of a staircase easily by just clicking two points on the stair.
To insert a railing along the center of a staircase:
Select Insert > Railings > Railing on Stair Center, or click the Railings button on the Building toolbar and select Railing on Stair Center.
In the catalog, select the railing type you want to insert.
Select a point anywhere along the bottom of the staircase (or along the tread where you want the bottom of the railing to sit) to define the level of the railing’s bottom post. Your cursor will snap to the center of the staircase as you start to draw the railing.
Select a point anywhere along the top of the staircase (or along the tread where you want the top of the railing to sit) to define the level of the railing’s top post.
Right-click and select Finish.