The Trinity Knot is a beautiful yet simple Celtic knot design representing eternity and unbreakable unity. It is also easy to form from wire with the right technique.
To break it down geometrically, the Trinity Knot is made up of 3 half circle (180 deg) arcs. You can modify the shape by changing the length of the arcs. Larger arcs (see 225 deg) form a rounder Trinity Knot, whereas smaller arcs (see 135 deg) form a pointier more triangular Trinity Knot. But let's stick with the classic 180 deg arc Trinity Knot.
To form a Trinity Knot from wire, start with a coil of wire, and place a bend in the coil every 180 degrees. The knot itself will require 1 1/2 rotations but we also need to add some length on either end for a wrapped eye closure. For my ~14 mm diameter coil, 2 rotations was the perfect length.
The trick to getting the knot to twist around itself is this first step of tucking each end of the coil under and to the other side of the coil.
Center the Trinity Knot (both leftover ends roughly the same length) by centering one of the half circle arcs on the coil. Find the spot that is ~1/4 rotation from the coil center, and bend the coil inward with chain nose pliers. Do the same thing with the spot ~1/4 rotation on the other side of the coil center and miraculously the Trinity Knot shape will emerge.
Use the remaining ends to place a wrapped eye at the top of the Trinity Knot to attach to other components. Start by bending one of the ends where it intersects the other and straighten it so that it is a stem pointing straight up. Wrap the other end around the stem a few times and trim. Cut the stem to the length needed to form an eye (10 mm in this case). Then bend the stem to one side and use looping or round pliers to form the eye.
You can add beads to one of the side arcs by threading the beads on one of the ends after the knot is first formed. Notice beads can't get past the bends to the center arc, so any beads intended for the center arc need to be threaded onto the coil before bending. Another option is to use finer gauge wire to wrap beads onto the finished Trinity Knot design.