Lateral wellbores intersecting a main wellbore are located with calipers on a tool. Each caliper includes first and second segments pinned to one another. Ends of each first segment distal from the pinned connections pivotingly attach to the tool. Ends of each second segment distal from the pinned connections couple with shuttles that slide axially along the tool. Biasing means urge the shuttles toward the pivoting connections of the first elongated segments to urge the pinned connections radially outward. When downhole and away from a lateral wellbore, walls of the main wellbore prevent the calipers from projecting into a radial maximum extension. When adjacent a lateral wellbore, calipers facing the lateral wellbore are extendable to a maximum radial extension. Distances between the pinned connections and tool are estimated with sensors; and openings to lateral wellbores are detectable based on the estimated distances. A steering arm optionally steers the tool downhole.