Abstract: A pneumatic nailer comprising a frame defining a fastener ejection opening, and an elongated driver chamber. The driver chamber in turn defines a peripheral wall, a first end away from the fastener ejection opening and a second end towards the fastener ejection opening. The nailer also comprises trigger member and a piston member movable between a first position and a second position. The piston member comprises a piston driver slidably mounted in the driver chamber. When the piston member is moved towards the first position, the piston driver is moved towards the driver chamber first end; when the piston member is moved towards the second position, the piston driver is moved towards the driver chamber second end.