These terminal blocks are used anywhere you need to connect wires together. Using a terminal block instead of butt connectors makes for a much neater junction that you can troubleshoot afterwards if necessary. These are standard duty blocks which are not as small and fiddly as the 2400 series and have a #8 screw. Rated up to 30 Amps AC or DC they are often found behind electrical panels, in ceiling voids where they are used for lighting power distribution, or at the base of masts where they make a connection that can be undone if the mast is unstopped. Using terminal jumpers allows you to join adjacent terminals together so you can have a single input wire feeding several branch circuits.