A mantrap is a highly secure physical control that consists of two sets of interlocking doors. An individual enters into the first door, and it must close and lock before the second door can open. This control effectively prevents tailgating because it limits entry to one individual at a time, and access can be controlled by various forms of authentication before allowing passage through the second door.

The use of signs is just a deterrent control and does not physically stop unauthorized access. A fingerprint scanner is an authentication mechanism that can be part of a mantrap system but on its own does not prevent tailgating. Security guards are a physical control but can be less effective than mantraps in completely eliminating tailgating as they rely on human vigilance and can be distracted or deceived.