A bougie for use in performing a gastroplasty to form a bypassed portion of a stomach and a stoma by joining stomach walls along an inner edge of the bougie, the bougie comprising: an elongate body shaped to follow a lesser curve of a stomach, thereby having a side with an inside curve and an opposite side with an outside curve, and having a distal end placeable near a gastro-duodenal junction of the stomach and a proximal end; an extension attached at one end to said elongate body and moveable between: a closed position wherein said extension lies along the opposite side and conforms to said elongate body; and an open position wherein said extension splays away from the elongate body, thereby forming a Y configuration with said elongate body to position the inner edge of the bougie, which is opposite to the lesser curve of the stomach, away from a gastroesophageal junction of the stomach, and leaving a space in a top of the stomach to allow communication between the bypassed portion of the stomach and the stoma; and said bougie being characterized in that it further comprises an activation mechanism comprising a sliding ring that passes around the outside of said bougie, between said bougie and said extension, but not including the extension, said sliding ring being movable along the bougie and useable to move said extension from said closed position to said open position, said activation mechanism further comprising an extending wire adapted to be passed through an internal lumen of the bougie and to exit the bougie through a port located distally of a distal end of the extension, said extending wire being then adapted to be routed proximally and attached to the sliding ring. an elongate body shaped to follow a lesser curve of a stomach, thereby having a side with an inside curve and an opposite side with an outside curve, and having a distal end placeable near a gastro-duodenal junction of the stomach and a proximal end; an extension attached at one end to said elongate body and moveable between: a closed position wherein said extension lies along the opposite side and conforms to said elongate body; and an open position wherein said extension splays away from the elongate body, thereby forming a Y configuration with said elongate body to position the inner edge of the bougie, which is opposite to the lesser curve of the stomach, away from a gastroesophageal junction of the stomach, and leaving a space in a top of the stomach to allow communication between the bypassed portion of the stomach and the stoma; and said bougie being characterized in that it further comprises an activation mechanism comprising a sliding ring that passes around the outside of said bougie, between said bougie and said extension, but not including the extension, said sliding ring being movable along the bougie and useable to move said extension from said closed position to said open position, said activation mechanism further comprising an extending wire adapted to be passed through an internal lumen of the bougie and to exit the bougie through a port located distally of a distal end of the extension, said extending wire being then adapted to be routed proximally and attached to the sliding ring.