Assembly for endoscopically securing gastrointestinal tissue folds, comprising a first tissue anchor and a second tissue anchor, a first suture thread part and a second suture thread part, each of the first and second thread parts having a connected end and a free end opposite the connected end. The first thread part and the second thread part are tied to each other through a sliding knot, such that the first thread part firms a post of the sliding knot along which the sliding knot is arranged to slide during tightening of the assembly and such that the second thread part wraps around the post to create the sliding knot. The first thread part extends from the first anchor to past the sliding knot where the first thread part's free end forms a post free end, and the second thread part extends from the second anchor to past the sliding knot where the second thread part's free end is free, such that the sliding knot is interposed between the first and second anchors. The first or the second anchor comprises a knot retaining through hole, wherein the post free end slidingly passes through the knot retaining through hole, the knot retaining through hole having a size preventing the sliding knot to pass through the knot retaining through hole, such that the anchor can be used as a knot retainer during tightening.