using keys formed of wire or other flexible material, to be inserted through an opening giving access to grooves in the adjacent surfaces of the parts to be connected

Full Title

Key-type connections; Keys (F16B2/00 takes precedence; for rods or tubes mutually F16B7/00) > using keys formed of wire or other flexible material, to be inserted through an opening giving access to grooves in the adjacent surfaces of the parts to be connected