Here's a larger wire holder type insulator with built-in lag screw. It carries a heavily-insulated piece of what looks like #8 or #10 wire. The tie wire goes through the eye of the insulator too, and appears to be lightly-insulated #10 also. I found three of these in the WEPCO dumpster in Kenosha, WI, after applying the "beer wrench" to the guys working there. I would think these were used to manage the positioning of a jumper wire, where there was no need to worry about mechanical loading on the wire, for example under a crossarm.