Devices and methods for tissue acquisition and fixation, or gastroplasty, are described. Generally, the devices of the system may be advanced in a minimally invasive manner within a patient's body to create one or more plications within the hollow body organ. A tissue treatment device attached to a distal end of a flexible elongated member and has a cartridge member opposite an anvil member. The cartridge member and the anvil member are movable between a closed position and an open position, and a moveable barrier is disposed between the cartridge and anvil members to help acquire a dual fold of tissue. The tissue treatment device can be repositioned to form multiple plications within the organ.