If any one one has seen one of these please let kevin (wright722@btinternet.com) know the location. They can be a cylinder as in this photo of one found in Tameside, usually with central pin or a central space so they can be rolled into place or much larger less mobile forms e.g. cube shaped. Of particular interest is a line from Warrington to Stock port and then northwards towards Rochdale. It could be anywhere with 10 miles either side of this. However any other sightings appreciated. They were often reused for land management e.g. around water ways. 
