One often overlooked aspect of childproofing is balcony, staircase and deck railing with spacing between the spindles over 3". This creates a hazard where a child could slip through the railings or get stuck within the railing. Another concern is children throwing toys or other objects through the railing to the lower level.
I have seen both interior and exterior railings which are unsafe for children. Railings that have horizontal crossbeams are easily climbed presenting a major risk of fall.
To remedy these dangers, there are a few very good options. One option is to keep the area off limits through the use of gates. The preferred method is to install crystal clear polycarbonate panels which are extremely strong and can even handle a gently curved railing.
For outdoor railings, we use a heavy duty mesh to line the railing.