I have seen these before and have a friend who just got some while out in the wild. Does anyone know the exact usage, name of the units, and what the rectangular looking parts are made of? Vic Wheeler said, "These are a type of cable "hanger" used to secure cable on an aerial messenger system that was typically used on the railroad back in the day. This type is a do it yourself style that probably was used on a line drop or in a signal bungalow. The insulated segments protected the bundled copper conductors from rubbing against each other during normal weather conditions. They were wrapped around several conductors and tied to a supporting steel cable either pole to pole or pole to bungalow. They were sometimes used inside a larger enclosure to neatly bundle conductors together. Several styles were used. In later years cable "lashing" replaced most of these types of hangers." John WIlson said "The ones that I saw were on the Boston Line, which runs between Boston, MA and Selkirk, NY. These installations were always relatively close to the ground averaging about 6 to 8 feet up and supported by iron or steel hangers from stone walls or concrete posts."