The idea of a tree house for our backyard was embraced wholeheartedly by our girls.  They were about 6 and 4 at the time and they enjoyed watching the progress as their Dad sawed and hammered.  They added their ideas about how to make the journey of getting up into the structure.  We liked the idea of an open front but wanted safety for young kiddos.  We opted for picket style rails so that kids could see out and parents could see in.  An arched doorway was made but we didn’t put in an actual door because we worried about smooshed fingers.  Shelves were added inside so that treasures could be stored.  A window was put in one side (we never got around to adding curtains).  Because this tree house is open we do have to sweep it out after bad weather but the slanted tin roof keeps kids dry during rain showers.