This is a mechanism that was used in several famous rifles. The original action was invented by one Henry Peabody and was used in the Peabody rifle. In this type of action, the breechblock is attached to a hinge on the rear of the block. When the lever is operated, the block tilts about this hinge and exposes the chamber of the rifle.
The above picture shows a Peabody rifle with the action open. The reader may observe the breechblock is tilted down towards the right, opening the chamber. Also note that the top of the breechblock is hollowed out to aid in inserting a cartridge into the chamber easily.
The picture above shows a Martini-Henry rifle. In the top picture, you can see the lever behind the trigger guard is opened, which opens the action and cocks the rifle. The breechblock is tilted forward, exposing the chamber. When the user pushes the lever back, as seen in picture B, the breechblock moves upwards and closes the breech.
In the picture above, the breech block is B and K is the firing pin mechanism. The top of the breech block I is hollowed out to assist inserting a new cartridge when the mechanism is opened. When the user pulls lever E, it moves the tumbler G, which makes B and K pivot about the pin C. The front end of B and K drop and expose the chamber J, where the user can remove the old cartridge and insert a new one. When E is pulled back, G moves and makes B and K rotate back up so that K is in line with J. When the user pulls the trigger, the hammer strikes the back of K, which moves the firing pin to strike the primer of the centerfire cartridge and discharges the weapon.