This is a beautiful ritual that goes back to Celtic times (technically, to Ancient Roman and Greek days). It is the origin of “tying the knot”. It involves (usually coloured) ribbons or cords being laid over the couple’s wrists, as they hold hands, and then tying them up (temporarily!).
There are various versions of handfasting (any of which can be chosen), so it can be the focal part of the proceedings or simply a delightful short ritual.
Some people choose to hold a handfasting in the Inner Circle at Stonehenge, which I can arrange, given sufficient notice. Another possibility is a ceremony in the public area, and that can be fantastic too!