Copper plated Britannia pewter TierraCast® 18mm round tribuckle for use with cording up to 5mm wide. Great for multi-wrap strap designs! TierraCast Safety Compliance Info. To use, rivet or knot cord on smallest opening, then thread other end of cord through the wider openings. Keep the buckle's ridge on the top side of your design — it helps keep the strap in place once buckled.