Upper and lower main gear box plugs
Upper and lower trans gear box plugs
Upper and lower axle plugs
= 1/2 inch square drive, you can stick a 1/2 socket wrench in there, obviously without any socket attached and turn. Make sure the 1/2 square is in there tight because some 1/2 inch drives are rounded a bit so sockets click into the easier.
1955 Series I
1994 Defender 90 #916
1967 Lancia Fulvia
1974 Alfa Romeo GTV