Instructions
Locate the top lever of the BT-99. This is the metal lever at the rear of the barrel where it meets the stock of the gun.
Slide the lever to the side to lock it. This locks the barrel bolt, which is fitted to the barrel lugs. This will lock the barrel and prevent discharge of the shell.
Slide the top lever to its original position when you would like to unlock the bolt and have the weapon discharge the shells.