Through-hole technology

Through-hole technology is when electronic components are attached to a circuit board by going through tiny holes drilled in the board. Kind of like when you put a pencil through a hole in a piece of paper.

The parts that go through the holes are called leads, and they have little metal legs that stick out on the other side of the board. The legs are then bent or soldered to hold them in place.

Through-hole technology used to be the most common way of making circuit boards, until surface mount technology came along. But sometimes through-hole technology is still used for bigger parts that need to be stronger or for things that need to handle a lot of power.