I thought I would throw in my 2 cents worth on this subject.
 
I was reading Betty's post about the one ferret she has that finally
discovered how to operate a staircase.  I had this happen to me just last
week.  My fuzzies have always contended with stairs.  In my apartment they
were carpet-covered and easy for the ferrets to use.  The house I bought has
an open staircase.  Open meaning there are no toekicks in the back.  I was
terrified that they would fall through the steps, especially on the way down
the stairs.  I thought about blocking the back of each step with plexiglass
(I really need them clear so light can go through or it's just too dark
under there.) and had blocked the entire staircase with a large uncut piece.
Fifi, aka Mountain Goat, proceeded to climb right over it and run up and
down the stairs.  I took the block off and all was well.  Five of the six
had no problem on the steps.
 
Timmy, on the other hand, never even attempted the steps.  He has an
enlarged spleen and is just a large clumsy boy in general.  He has a hard
time even jumping into the bathtub for a drink or getting on the couch.  A
few days ago, I set him down on the second step before I went out to get the
mail.  When I came back in he was all the way upstairs.  I was really afraid
that he would be the one to fall on the way down, so I promptly brought him
down, hoping he would forget all about the upstairs room.  No chance.  The
last few days have been nothing but up, down, up, down, up, down, up down.
If he's missing, I know to look upstairs.
 
I can also tell exactly who is going up and down by the sounds.  It can be
completely dark, or I can be in another room, and the speed is a dead
give-away.  So far the only casualty of a fall has been the graceless cat!
 
Debi and the "stair struck" sharks
Fifi, Moose, Jiggy, Lily, Gaby, and Timmy (Looky!  I can climb the stairs!)
and Puppy the stumbling kitty
[Posted in FML issue 3014]