Device and method for determining parameters of blind voids

Device for determining the size of a blind void comprises an elongated rigid rod, an actuator slidably movable relative to the rod, the actuator having a distal end for insertion into the void, a distal flexible element fixed at one end thereof to the rod, a second flexible element fixed at one end thereof to the rod and proximally removed from the distal flexible element. Movement of the actuator is operative to cause equal movements of the distal end portions of the distal and proximal elements, to cause the distal element to bulge outwardly from the rod to engage interior walls of the void and to cause the proximal element to bulge outwardly in a configuration duplicative of the distal element bulge, the proximal element being outside of the void and subject to observation.