Activists lock on across the road at Aberthaw power station in an action I helped with. The tubes are bits of metal pipe with pins welded into the centre. You then attach yourself to the pin. The police have to cut you out with an angle grinder, or some special long-nosed clippers.
See:
www.indymedia.org.uk/en/regions/oxford/2008/04/395459.html
www.indymedia.org.uk/en/regions/oxford/2008/04/395493.html
thecoalhole.org
