A positioning system having a base, a manually movable end effector and a first joint interposed between the base and the end effector is disclosed. The first joint may comprise a proximal portion and a distal portion coupled together by magnetic attraction and configured to be intermittently separated by a pressurized gas cushion. The first joint may be configured to be changeable between a movable state and a fixed state. In the movable state, the proximal and distal portions are separated by the pressurized gas cushion and are movable relative to each other. In the fixed state, the proximal and distal portions contact each other and relative movement is thereby impeded.Methods of precisely positioning an end effector may include providing a device having a base, a first joint located distally from the base, and an end effector located distally from the first joint. The first joint may have two portions separated by a gas cushion, the first joint allowing the end effector to be movable with respect to the base. The method may further comprise manually positioning the end effector, and removing the gas cushion to cause the two joint portions to contact each other, thereby locking the end effector in the precise location in which it was positioned.
