When I add a 'prop' to a scene, I can typically grab it in VR at any point on its surface, as if I were grabbing it with my hand, while 'shapes' only seem to be grabbable by their control handles. What do I need to switch on the shapes to make them behave more like props? I'm trying to make some props out of basic shapes and would like to be able to move them around in play mode in a more natural way.