Yellow security rope. The kit offers only a relief + a yellow decal. I replaced both with 0,4 mm wire, flattened on the end (plus a 0,28 mm hole) and yellow thread.
As promised here is the description about my “new” technique for small round windows. I used the 0,04 mm thick foil applied on the smartphone “bulletproof” glass as protection. Punched small disc with flat needle and brass tube. The edges of both tubes sharpened with cone shaped milling head.