A takedown screw for a 10/22....but here's the kicker; extended out and fastened into a short, round knurled vert grip. Mine, I just took a short section of threaded stock (barrel V-block screw) and epoxied it into a short black screwdriver handle. I'd like knurled synthetic to match the standard Rugar synthetic stock. Eliminates a tool for field takedown. Allows me to use a cut down stock with no forearm. Mine's cut 2" in front of the takedown screw. Makes the unbarreled action, receiver and stock fit into a good, small package for stashing or pack carrying. This was long before the takedown model. Mine's smaller.