Hex bit retention, Proto 5441 1/4

[ChevyEFI]

I hit the Glendale swap meet and these came home with me. Socket, no bit. They're drilled through. What originally held the hex bit in place?

 

[LXCam]

Roll pin. All my proto sets are that way.

 

[Zewnten]

The dimple some manufacturers, snap on bondhus, put on the end of hex bit also works