If you want to connect customized power supply to your project board with a DC jack, this adapter can be very useful. With this adapter, you can custom your own cable length and thickness for power delivery. The DC plug is a common 5.5mm x 2.1mm male plug on one end with center positive connection (the most common).

On the other end, there is a screw terminal block where you can insert your wires in. The polarity of the terminals are embossed, positve (+) and negative (-), so that there is no guessing work needed there.