From the Annals of Screwing –  In 1882, the Screwmen’s Benevolent Association called a general holiday (actually a strike)  for its members in opposition to the appearance of black workers in the cotton-screwing trade.  The SBA was a trade union of specialized longshoremen who used screwjacks to stow and pack cotton bales into the holds of ships.  The screwmen were almost entirely whites of various European origins and opposed allowing blacks to practice their trade. The SBA used an apprenticeship system to exclude blacks and gain a virtual monopoly of the work at the port of Galveston. After the invention of the high density cotton compress in 1910, the need for screwmen was gone and the SBA faded into history.