If the door is CLOSED on the ferret room, the gate prevents them from
getting out at the bottom where there may be a gap between the door and
the floor, which is what the original "poster" was inquiring about.  If
the baby gate is in the doorway with the door OPEN, yes the ferrets will
climb it.  But we took care of that by covering the gate with a piece of
cardboard (either hot glued on the frame or duct taped) and that solved
any and all climbing.
[Posted in FML issue 4799]