I don't have to baby proof anymore, but for those of you that do, I think this is genius (if you have lever doorknobs). Staple a length of ribbon to the top of a door and tie it to the knob. Door will only open if you push up on knob, so little ones can't pull down and get the door open. :)
The bauhaus lever door handles on a flat square face fixing rose. Spring needs to be bored into the door. Finish in antique brass, which looks stunning with the sharp edges and rounded grip. A very contemporary and modernistic handle. Available in full length back plate versions as well.