Through hole

For the electric circuit fabrication technique, see Through-hole technology.

A Through Hole refers to a hole that is reamed, drilled, milled etc., completely through the substrate. In other words, a through hole is a hole that goes all the way through something. This is to distinguish it from a Blind Hole, which does not go all the way through the substrate.

A possible analogy of this would be a bullet shooting through a wall. If it completely penetrates the wall, leaving a hole visible from the other side, then this is a through hole. Conversely if the bullet is stuck, and does not fully penetrate the wall, then it leaves only a blind hole.