External fixators are robotic devices widely used in orthopaedics. While bringing the bone fragments to a desired position, these devices should not present any threat to the patient health. One of the threat causes is singularity. In a singular position, stable structure of the fixator is lost and its top and bottom rings may move independently. In this work, singularity analysis is performed with a geometric method, closest points approach. It has been shown that results of this approach are consistent with the other singularity analysis methods.