I'm a complete clutz when it comes to computers and cameras, so rather than screw things up I'll describe the bayonet I've got sitting on the desktop in front of me. First off, you're right, the bayonet would preclude a cleaning rod beneath the barrel. The stock slot beneath the 91/38's barrel is for the bayo's folded blade. The 91/38's cleaning rod was a sectioned deal carried in the butt trap. The bayonet itself has two spring-loaded buttons; one on the right rear is for locking onto the rifle's bayo stud, the one on the left just below the bayo's barrel ring is for unlocking the blade from its open or closed position. With the blade extended, push inward on the left hand button, pull the blade forward, rotate the blade downward and through 180 degrees until it sits in the stock's slot, then push the blade forward to lock it in the closed position. To open, push button, pull blade to the rear, rotate through 180, and once extended push to the rear to lock in place. They aren't the sturdiest things in the world, and just about every one I've ever seen rattles to one degree or another, so it's little wonder that late variations were pinned open. I think milsurp.com has an Italian arms section, so someone there could probably help with photos or a decent line drawing.