An automatic locking mechanism for use in a power return tape measure includes a user-accessible actuator, a brake element, and a biasing member normally urging the brake element into contact with the tape drum. In a locked position, the brake element wedges against the drum. The actuator displaces inwardly to move the brake element out of contact with the drum. A rotatable coupler/member may convert pivoting motion of the actuator into brake member translation. The coupler may include first and second arms that respectively contact the actuator and the brake element. The coupler may further include a cammed outer surface that contacts the drum in the locked position. The cammed surface rotates out of contact with the drum in the release position. The cammed surface of the rotatable member may be used independently of, or in conjunction with, the brake element. Related methods are also described.