If I had known this project would turn out so well, I would have taken photos as I went. The drawing shows a block of steel about 1/2 inch by 1/2 inch square with a tapped hole to receive the forearm screw. My best guess is that the screw was turned partially into this block attached under the barrel of the gun when the gun or the barrel was dropped and the screw absorbed the impact. Anyway, the screw would turn into its receiver only about three turns before it would go no farther. The result was that the forearm stock was loose on the barrel.