assembly for holding a substantially flexible implantable suture guide in a substantially taut position for suturing along a suture line having a desired shape or dimension such as the desired circumference to which an enlarged heart valve annulus is to be reduced by the formation of pleats about the base of the valve annulus the suture guide of the invention is formed from a freely flexible rib encased within a woven cloth covering in use the flexible suture guide of the invention is held taut by the holder assembly and in a configuration determined by the shape of the holder assembly while the surgeon uses the support provided by the taut suture guide to evenly place the sutures and to draw the tissue by means of the sutures passed through the suture guide into a suture line having a shape substantially similar to that of the suture guide and holder for example for use in annuloplasty the holder assembly can be c shaped so that the suture guide temporarily affixed thereto assumes a c shaped configuration the suture guide can then be sutured to the base of a heart valve annulus so as to restrict the circumference of a dilated and or deformed valve annulus to a more normal one.