From the time that I bought my 71 280SEL, the rear driver side door wouldn't open from the inside. I gave up trying to figure out what was wrong with it. But last summer when I re-did the door panels, I tried to fix it, with the panels off. Everything seemed to be in order, but it just would not open. This wasn't that big of a deal because it opened fine from the outside. Well, yesterday I was cleaning up the door catches on all four doors. Low and behold, when I got to the back doors I noticed a little knob on the door catch. I thought hmmm, these weren't on the front doors. So I tried to push it in, nothing. Then I tried to push it back and forth, and it moved. All of a sudden it hit me. This is just like the buttons on my 97 dodge and my 2000 pontiac. It's a safety child lock. I'm not writing this because I think I made a new discovery that nobody else knew about. I just can't believe I'm such an idiot, that I didn't figure this out before. But I would have never guessed that in 1971, a feature like this would be on a car of any make. Although I like to think of this as a "Mob" feature. Ya know, you pick up the guy that's been ratting out your boys, so you can have a "talk". This way your assured he won't be able to escape.