Here are four styles of spare tire locking straps. The one with the "T" notch is possibly used on commercial vehicles, interlocks with the spare tire hoop. Maybe Oldandtired could chime in with his opinion. The other three are for 1937-38 passenger cars. The strap with the extra piece on the cup is used with the "L" bolt so no one can get at the cotter pin to remove the strap. The straps with flat bottom cup would be used with the blind nut in the floor pan or island between the trunk boards. The channel type in addition to 1937 car is one of two types used for 1940 convertible but cut shorter. There are three styles of locking nuts shown. The nut with its own 5/16ths stud is used with the "D" nut in the floor, the locking nut with 5/16ths thread is for the "L" bolt type. and the other nut is used on a wheel stud.