Grasp an awkward rigid part by the waists in its own silhouette — take the alpha shape of its point cloud from above, find where that boundary turns inward, and close the jaws across a pair of those inward runs. Use when a part has no graspable long axis and no pair of parallel walls an OBB would find — pliers and scissors gripped at the joint, a spool at its neck, a gear between two teeth, a bulb socket at its skirt. Use grasping-linear-feature instead for handles, rods and shafts, and grasping-short-axis when an upright box is enough.
