Our "bridle" wire is a twisted pair that would use as a jumper from an aerial terminal to a six pair block mounted on a pole feeding a 6pair drop or from an aerial terminal to a 107 block on "C rural" wire. It is basically just a heavier and thicker jumper wire that could be exposed to the elements.
Here's a question for you no one has been able to answer for me in 38 years of telephony, why in: drops, IW, Central offices, is it "Red, right, ridge=Ring" but in cable Red is a tip color and green is a ring color so in a ready access terminal you would splice the Green/Red pair to the Red/Green in the drop?
Also goes to show that the yellow and black weren't meant to be a pair when they came out with the 4 wire IW, they are both Tip colors.
Pair 8 is Christmas, pair 12 is Halloween. Different perspectives from different areas.