I support the people mentioning getting a good guard dog, particularly a LGD. Not many people would want to mess with one. I don't lock my barn, but my male collie has patrol of the property at night. He is a very, very good LGD, has has driven away intruders before. I do have padlocks on my pasture gates, at the advice of my insurance company, since I had someone come into my pasture and get injured once. Although the padlock wouldn't stop anyone from coming through the fence, apparently in the law's eyes, it makes the difference between general and criminal trespass. Strangely.