Someone gave me this picture and asked

"Apparently it was used in the stringing of open wire but I'm not sure how it was used. I was a telephone lineman for almost 40 years but was never involved in stringing open wire, only removing it. I'm not sure if you can see it but there are three spring loaded devices that can put the centre section in different positions. Perhaps you or one your fellow collectors could shed some light on it."

Any thoughts?