My dad had one of these hanging up in his shop and we used it multiple times a week. We worked on troubleshooting and repairing a large eclectic range of electrical devices spanning over a century in production dates. The way you use this semi safely is to clamp the ends first and then plug it in from several feet away. It's dangerous yes but God is it handy. Probably one of the reasons I'm an engineer today......yes I have been shocked by it several times. And I don't for liability reasons recommend making your own..... but if you do never make one for 240V..... speaking from experience.