Choose a terminal block by matching the circuit function, connection method, rated current, rated voltage, wire size, conductor type, housing material, mounting method, and required standards. A terminal block is not selected only because the wire fits into the opening. But when procurement emails ask whether to use screw terminals or spring-clamp, or when specifications list “barrier blocks” without context, clarity becomes critical. They connect right to printed circuit boards. This saves space and makes wiring simple.