AtD translation: brakebeam stiff

[Mike Jing]

P465.7-13   . . . Frank ran into the Reverend Moss Gatlin driving a
strange-looking horseless trolley car, with a miniature steeple and working
church bells on the back end, and over the front window, where the
destination sign usually was, the lighted-up words anarchist heaven. Moss
was busy picking up every vagrant, ankle-biter, opium fiend,
down-and-outer, brakebeam stiff, in fact any citizen looking even a little
helpless—and loading them on board his A.H. Express.

What exactly does "brakebeam stiff" refer to?