Re: Oneway screws
most extension blocks in the UK use these nasty pieces
If you can't get them out by simply applying vertical force while turning them; the heads can usually be drilled away, the extension assembly pulled apart, the screws removed with a Mole Wrench.
They are mainly for health and safety, to stop idiots taking apart things they shouldn't be taking apart.
Mine's the one with the cut-down 6" nail 'fuse' in the pocket.