As an example: a simple hodoscope might be used to determine where a particle crossed a plane or a wall. In this case, the experimenter could use two segments shaped like strips, arranged in two layers. One layer of strips could be arranged horizontally, while a second layer could be arranged vertically. A particle passing through the wall would hit a strip in each layer; the vertical strip would reveal the particle's horizontal position when it crossed the wall, while the horizontal strip would indicate the particle's vertical position.