through-hole

A through hole, also thru-hole or clearance hole, refers to a hole that is reamed, drilled, milled etc., completely through the material of an object. 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 material of the object.

Through-hole technology, also spelled "thru-hole", refers to the mounting scheme used for electronic components that involves the use of leads on the components that are inserted into holes drilled in printed circuit boards (PCB) and soldered to pads on the opposite side either by manual assembly (hand placement) or by the use of automated insertion mount machines.