Unfortunately these specimens and their bracket have been painted to match the woodwork.
This insulator is used at the lower end of an arrangement to bring a pair of open wires down a high building to a lower point where they can terminate on the lead-in cable at a convenient height for fault finding. The upper point uses the Insulator No. 10 also with side knobs.
The insulator measures 2¾″ in diameter and 4½″ high. The top recess for the connectors, under the screw cap is ½″ deep and 1¾″ diameter. Two ⅜″ holes drop out of the recess for the terminating cable(s). Just above the top groove is a single ⅛″ hole for the copper wire to enter the recess. These dimensions are the same as the No.16, but this insulator only has a single main groove. The knob is 1⅝″ in diameter, sticking out ⅞″
