If you want to find some other links (humans love to do this!): that pattern is found on hinges, latches, and other bits of metalwork and woodwork near openings in to houses (such as chimneybreasts), and is interpreted as the Day Rune (Dagaz), and as protective mark against witches (scroll down this to about page 16, which is a paper on the subject by Timothy Easton http://planning.babergh.gov.uk/doldp/27785_2.pdf)