bascules

Noun

bascule (plural bascules)

1. A counterbalanced structure having one end that rises as the other lowers.
   • In the late eighties and early nineties several new types of movable spans were advocated, including the pull-back draw, the jackknife span, the bob-tail swing, the horizontal-folding draw, the shearpole draw, the gyratory lift, the transbordeur, the double-cantilever swing, several types of...1932, Journal of the Association of Chinese & American Engineers, page 10
2. The portion of a breech-loading firearm that pivots open in order to allow access to the chamber.
   • A device for coupling and releasing the trigger mechanism in a bascule of a gun1997, Official Gazette of the United States Patent and Trademark Office