Building a Stairwell

This will show you how to build a basic  set of
stairs and explain the cloning feature.

The first step in making stairs is to make the landing which 
is done simply by making a brush against one of the walls in
your map.  The height of the landing should be appropriate
for whatever your using it for such as a new level or maybe
a new doorway.  Then with the brush still selected hit the
'space bar' and you'll see a clone of the brush appear.  It
will move slightly from the original brush and will now be
the selected brush.  Make the new brush ten units high
and ten units deep.  Leave the width the same as the 
original landing brush.  This will be your first step.  Now
line up the new brush below the landing as pictured
below.  Once the brush is in place you can clone the new
brush again by hitting the 'space bar' again.

   

Now repeat the process again by moving the new brush below
the second one.  Just repeat the process until you've reached
the floor.  Now the bottom stair will probably be slightly above
or slightly below the floor level of your room.  Just move the 
bottom of your last step to match the same level of the floor
brush by making it shorter or higher.  Now on to the side
rails.  This time create a new brush along side of your new
creation that rests flush with the back wall and floor.   Bring
it out around ten to twenty units beyond the last step and
then hit the 'e' key.  You should see little blue dots appear
along the edge of your new brush in the wireframe window.

   

This is called the edge tool and it allows you to manipulate the 
edges of any brush.  By selecting the blue dot on the corner that
sits above the last step, you can pull down that end so that it runs
at an angle along the stairs.