Keep away from balcony railings anything that can be climbed on. In fact, keep these things off balconies altogether unless they are too heavy to be moved near a railing. Kids don't have an in-built sense of danger - especially young ones, and climbing is so much fun for them to do. If you have a table and chairs on your balcony, consider either fixing them down (away from the railing), attaching them to something (away from the railing) or using child-proof locks and gates on all accesses to the balcony. Locking off balconies is recommended regardless of the other safety precautions taken. Children are incredibly adept at finding ways to do things, like climbing over railings.