It is advertised for "timid, arthritic or aging dogs"...I have 6 dogs and spent an entire afternoon trying to get them used to the clanking sounds and seriously-swinging door. All 6 dogs have been using a rubber flap dog door for years; I purchased this door for it's generous width. They weren't timid before, but now they are. Finally, I got one dog to start through this thing on her own, without holding the door up. As her rump cleared the door, it swung down and caught her hind leg just above her heel, trapping, frightening and hurting her.... Timid and arthritic and aging dogs beware! This dog door is also a flat, single frame and swinging dog door--no other frame for the other side of the wall or house door you are trying to attach it to, no hardware, no inside framing. Expect to do carpentry work for installation.