Security guards function as a deterrent to trespassers, burglars, and vandals when you have the right people and use them effectively. Using human personnel to watch over your property only makes sense if you have a large area that needs surveillance because of the high cost and maintenance that an employee requires. Guard services are frequently practical for businesses or for properties that have multiple buildings. However, using the wrong people negates any potential advantage having a security guard brings you.
Guards who are intelligent and well-trained also recognize potential hazards and security risks, allowing you to deal with them before they can be exploited. A good guard reports anything wrong with the property and can fix a lot of simple problems himself while on duty.