Green’s Dictionary of Slang

(US und.) the swindling form of ‘gambling’ known as the shell game under shell n.; thus hull joint, the equipment (three shells, a pea, a flat surface) required for the game to be played (usu. in the street).

1905		F. Hutchison Philosophy of Johnny the Gent 7: ‘She could take me, hook, line an' sinker, faster'n a yap goes for the hulls!’.
1905		F. Hutchison Philosophy of Johnny the Gent 55: No more chance fer that to happen than there is for a boob in front of a hull joint!