Then you move down to the Democratic Party line, the Republican Party line, and the Socialist Party line in which you would vote for Roosevelt.
And when you're done voting, you open the curtain, the levers return to the neutral position, the curtain's now open, and it's ready for another voter and at the end of the voting, end of the day's voting, the machine would be opened in the back, the full-size machine, and the numbers would be tallied and recorded by hand.
Source
Interview with Larry Bird, Smithsonian Institution's National Museum of American History, May 31, 2006.