I doubt he is looking for something that he has to put on and take off each time... I think he wants something that stays on the rifle, linking the upper and lower together so that when the rear takedown pin is pulled, the upper does not pivot to where it is perpendicular to the lower... Wants it to open just enough to reload easily. I've never seen such a device though, and would think having the upper fully pivot out of the way would be easiest.