A look inside the Cliff Quicktest mains connection unit.

The Quicktest unit has been around for a long time, and is used in electrical and electronic workshops to safely connect power to electrical equipment that does not have a plug. Note that the device is only intended for people with good electrical awareness.
It has a very strict isolation system whereby lifting the lid to access the terminals completely isolates the live and neutral connections.
Connecting the test wires is done via "piano key" type connectors that grip the wires securely when released. The connectors are colour coded with the standard European flex colours with the earth/ground key being solid green as opposed to striped green and yellow.

Since I get asked about this item a lot, here are some links to the manufacturer and suppliers.

Cliff Plastic Products:- http://www.cliffuk.co.uk/products/tools/quicktest.htm

US supplier:- http://www.newark.com/cliff-electronic-components/cl1850/electrical-tester/dp/68C8457?ost=quicktest&selectedCategoryId&categoryId=800000005787

(Suggested by YouTubers SolarDrew and Kasey Norman.)

UK suppliers:-
Rapid Electronics:- http://www.rapidonline.com/cables-connectors/cliff-cl1850-quicktest-mains-connector-23-0195

CPC:- http://cpc.farnell.com/cliff-electronic-components/cl1853/quicktest-mains-connector-block/dp/PL10638?ost=quicktest&selectedCategoryId=&categoryName=All+Categories&categoryNameResp=All%2BCategories