The bloomery , site 67 on the survey, is on Hollin How at GR SD 22511 97229 has been given rating of High for Potential, Value, and Rarity and 1 for Significance
Despite the uncertainty of any features revealed by this survey, Grassguards is nevertheless an important site. The slag mound is of unusually large size and is broadly comparable to the well-known slag heap at Springs, Coniston.
Taking a mean height for the slag mound of 1 metre, the approximate volume of slag at Grassguards is of the order of 270 cubic metres, representing some 250 to 300 tonnes of slag. Though this is less than half of the estimated weight of slag at Springs, it is clear that Grassguards is one of the larger iron-working sites known in Cumbria.
It can be estimated that 250 tonnes of slag could result from some 10,000 smelts. If 250 smelts were carried out each year, this represents some 40 years of continuous production. If two furnaces were being used simultaneously, there could have been 20 years of continuous production.
The iron-workers would have taken advantage of local timber supplies for charcoal making.