[ main_cnr_pos[0], top_z ],
[ side_thick, main_cnr_pos[1] ],
[ side_thick, -side_height ],
[ side_taper, -side_height ],
[ 0, -rivet_posn ],
[ main_cnr_pos[0], top_z ],
[ side_thick, main_cnr_pos[1] ],
[ side_thick, -side_height ],
[ side_taper, -side_height ],
[ 0, -rivet_posn ],