The recent development of compact surgical robots and instrumentation raise the need of a suitable mechanism for positioning and support in the proximity of the operative field. The accuracy of the surgical instrument and surgical procedure heavily relies on the ability of the supporting device to provide a sturdy base under the payload and dynamics of the instrument. We present a compact and sturdy passive mechanical arm equipped with a central braking system that can be easily manipulated to desired locations and firmly locked in place. The arm presents serial link architecture comprising two links and three joints: spherical-rotational-spherical. To ease the maneuverability of the arm, one degree of freedom of the spherical joint at the base has been blocked, yielding six overall degrees of freedom. The novelty of the arm relies in the special design of the braking mechanism that simultaneously locks all the joints using one single electric motor. The arm design is simple yet safe. One of its safety features is the power-fail-safe design rendered by the normally locked braking mechanism unlocked by a low-voltage electrical actuator. The arm is designed for stand-alone use in the operating room as an independent module, representing the latest member of a growing family of surgical robotic modules under development at our institution.