L’Arbre à Clous (The Nail Tree) is a surviving folk tradition in the Liége region. Going back to ancient tree worship (I confess to a Shinto leaning in that direction), Wallonians believed ailments could be transferred out of the body and into a tree by means of a nail. The idea was that the tree absorbed the illness and carried it down into the earth through the roots. It was thought best to carry out the ritual at night or on the north side of the tree. Rather than cut down the sacred trees, local religious culture sometimes attached shrines to them and they stood outside churches or pilgrimage sites.
Inside the Wallonia Museum behind a dense wire mesh there is a lightning splintered section of the Tilleul de Soleilmont, a gigantic linden tree near Gilly in Wallonia that is estimated to contain around 70,000 nails. It was struck by lightning in 1922, likely because of the metal embedded in it.
The museum had a graphic description of a person afflicted with a toothache who gouged at his gums with a nail and then hammered it into the tree. He claimed his pain disappeared.
Severe acupuncture recommended for only the most desperate. But listen, the pounded metal testimony speaks for itself.