faller-wire

from The Century Dictionary.

• noun In a mule or slubbing-machine, a horizontal bar which depresses the yarn or slubbings below the points of the inclined spindles, so that they may be wound into cops upon the spindles in the backward motion of either the billy or the mule-carriage.
• noun In a silk-doubling machine, wire by means of which the motion of the bobbin can be stopped if the thread breaks.