Steelyards are first rate and accurate weighing devices, intended to measure the weight of heavy objects. The object to be weighed is hung on the hooks on the short end of the lever and then a weight is slid along the yard length until the whole lever is horizontal. The scale on the yard is in units of weight (for scientists that ought to say mass) so you just read off at the point the weight has reached to balance the steelyard.
The one we have in the museum comes from a butcher’s shop and was clearly intended to weigh carcasses of meat.

Butcher’s steelyard at Market Lavington Museum
It has clearly seen better days but rest assured it was in that condition when it came to the museum. This one is marked ‘Crown Regulation 1926’ which suggests it is in the region of 90 years old/ It can weigh up to 300 pounds – about 137 kilograms.
This item is on display in our trades room at the museum.