I like a bit of law and this is an interesting case. A flagger was injured by a defective flagstone. His employer, Liverpool council, argued that they weren't vicariously liable for the manufacturing defect in the flagstone as they would be for tools etc under the Employers Liability (Defective Equipment) act 1969 as, in their opinion, the flagstone was materials and not equipment. It was found that for the purposes of that act the flagstone was equipment.
Theres a short write up here