This item was recently given to us at Market Lavington Museum. It came, originally, from Vicarage Farm in Easterton.

Rope tension weight for use with horses in stables
This is a roughly made metal ball, a little smaller than a cricket ball, with a large hole right through it. It had an agricultural use in the days of horses.
Imagine a horse tied up in a stable at the end of a hard day’s work. It needed to be able to sit or stand and have some chance to stretch its legs. But if given a long rope there was a chance it could get its legs tangled in it which would do it no good at all.
The solution was simple. The lead from the horse was passed through a substantial loop fastened to the wall. Then the lead was passed through this ball and then the free end of the lead was fastened to the wall. The sketch below might give the idea.

Using the tension weight
The weight on the rope meant there was always a small amount of tension that kept it taut near the horse. Of course, the horses were hefty farm animals used to hauling heavy loads. A metal (sometimes they were wooden) ball on a rope was no problem to such a beast.
Thanks to Philip and Elizabeth for this interesting item.