A utility arm includes a first arm, terminating in first universal joint, locked by a first piston, and a second arm, terminating in second universal joint, locked by a second piston. These are joined by an intermediate joint positioned between the first universal joint and second universal joint, and there is a locking means on the intermediate joint. The intermediate joint has a first housing, with a first pressure piece having an inclined surface which abuts the first piston, the first pressure piece having a conical or frustoconical surface a second housing, with a second pressure piece having an inclined surface which abuts the second piston, the second pressure piece having a conical or frustoconical surface. The first pressure piece and second pressure piece interlocks with corresponding conical or frustoconical surfaces, so that pressure exerted by the locking means presses the first pressure piece and second pressure piece together, such that the inclined surface of the first pressure piece acts on the first piston to lock the first universal joint, the inclined surface of the second pressure piece acts on the second piston to lock the second universal joint, and the corresponding conical or frustoconical surfaces lock the intermediate joint.

A utility arm includes a first arm, terminating in first universal joint, locked by a first piston, and a second arm, terminating in second universal joint, locked by a second piston. These are joined by an intermediate joint positioned between the first universal joint and second universal joint, and there is a locking means on the intermediate joint. The intermediate joint has a first housing, with a first pressure piece having an inclined surface which abuts the first piston, the first pressure piece having a conical or frustoconical surface a second housing, with a second pressure piece having an inclined surface which abuts the second piston, the second pressure piece having a conical or frustoconical surface. The first pressure piece and second pressure piece interlocks with corresponding conical or frustoconical surfaces, so that pressure exerted by the locking means presses the first pressure piece and second pressure piece together, such that the inclined surface of the first pressure piece acts on the first piston to lock the first universal joint, the inclined surface of the second pressure piece acts on the second piston to lock the second universal joint, and the corresponding conical or frustoconical surfaces lock the intermediate joint.