Sorry martin dont know if steel or plastic and unless I see the electrician when I fit the kitchens or he has done the same with the upstairs joists I may not find out. Thanks for everybodies comments it would seem that it is just the electricians own querk and not a reg. B.A.S.s cable tray made me think though, I seem to remember someone on this site with pictures of cable tray in a loft to keep the cables out of the 300mm deep insulation which seemed quite a good idea. I must have a look if the sparks have done anything like that when I get back to the site