Heavy duty rectangular connectors are designed to accommodate large electrical loads and direct signals under a multitude of operating conditions. They can be used indoors or outdoors and may provide some protection against the ingress of wind, sand, dust and water. Common features for heavy duty rectangular connectors include adherence to military specifications, custom designs, gold-plated contacts, and suitability for cryogenic use. Some heavy duty rectangular connectors are hermetically sealed or washdown capable. Others are weatherproof or washdown capable.

Heavy duty rectangular connectors can use either pins or sockets. A male type connector uses pins to make electrical connections. A female type connector uses sockets to make electrical connections. With heavy duty rectangular connectors, the number of contacts is the number of conductive elements which mate with a corresponding element to provide an electrical path. An electrical contact is the termination of an electrical wire in the connector's pin or socket. Contact size or termination size s the maximum diameter wire a heavy duty rectangular connector can accommodate.  

With heavy duty rectangular connectors, w ire size is measured according to the American Wire Gauge (AWG) standard. The AWG is used to measure certain conductors including copper. The higher the AWG number, the thinner the wire. This is because AWG stems from a measurement that represented the number of times the copper wire was run through a wire machine, which reduced the diameter of the wire. Thus, 24-gauge wire went through the machine 6 more times than 18-gauge wire.

Common termination options for heavy duty rectangular connectors include insulation displacement, solder cup or solder, screw, lugs, crimp, cage clamp or wire wrap. Important specifications to consider when searching for heavy duty rectangular connectors are maximum rated voltage, maximum operating current, and approvals. The maximum rated voltage is the maximum voltage that a heavy duty rectangular connector can safely transmit. The maximum operating current is the maximum current the connector can safely transmit. The maximum current or voltage rating for heavy duty rectangular connectors may be different from the supplier-designated maximum. In some cases, the heavy duty rectangular connector can be used safely at an unapproved level, but check with the supplier for specific usage details.