We've gone to great expense and effort to totally puppy proof our front deck for our babies so we can let them out safely and not have to worry about them escaping under a deck rail or through the spindles or something...there are locking gates at the steps and opening to the front yard and added wood under the rails so they can't get underneath. We never let them out alone but we do sit out there with our babies in nice weather and it has to be safe.
Anyway, just a few minutes ago my husband looked out the front window and said 'There's something big and black in our front yard...it just jumped over the deck rail from inside our deck'. I thought he was seeing things so he turned on the front light and there was a huge black lab standing there...he had just been on our deck! If I had opened the door and let my babies out before me he might have gotten one of them. I never thought I'd have to check out my totally enclosed deck before letting them out but I guess from now on I'll have to.