[Ron Wood]

(I see that Policeluger can type faster than I can, but here is my answer anyway)

Doug, the small wire in the frame is the spring that engages the groove in the takedown bolt and holds it in the closed position when you rotate it up. When you insert the bolt from the left side of the frame, you must press down on the bolt to compress the spring enough to allow the end of the bolt to enter the hole in the right side of the frame. It may take a bit of downward pressure and some wiggling to get the bolt to cooperate, but it will go. Please don't wack it with a mallet as you may well end up with a two-piece takedown bolt which will ruin a serial numbered part, not to mention the fact that it won't work anymore.