As reported in the International Business Times:
Witch markings dating to the 17th Century have been uncovered by archaeologists at a stately home in Kent and are believed to have been created to protect King James following the gunpowder plot of 1605.
Experts working at Knole house discovered the witchmarks in a room built to accommodate royalty. They had been hidden for centuries in beams and joists below the floorboards and on a fireplace in the Upper King's Room...
The witchmarks, or apotropaic marks, are carved intersecting lines and symbols believed to form a "demon trap" to ward off evil and prevent demonic possession. The marks include chequerboard and mesh designs, as well as interlocking V-shapes on the beams and joists – a symbol that stands for Virgo Virginum that invokes the protection of Mary the Mother of God.