It was a multi-page document 'fitting a forend', of which is probably the key instruction :
DO NOT LIFT THE FORE-END AWAY AT THE MUZZLE. Not now, not tomorrow, not EVER. It is only EVER tapped free downwards, at the rear, by finger pressure or tapping it downwards and free with a wooden drift against the top left and right edges of the fore-end. Thus, releasing it from the grip of the draws and the butt socket. This should tell you something. If your fore-end can be rotated free by lifting it away at the muzzle, then it’s well and truly shagged. That’s another REME technical term this time, meaning ‘ ….somewhat worn out!’