The male stands simply enough in regulation grey. It has two tall slab sides, an informed roof, and three red lights which continually flash in dumb warning. As might be expected, the short female is more complicated. Broadly built like a tin house, she reveals a square doorway filled with dangling black strips of rubber, able to let bulky belongings through onto rotating belt, first, and then a marshalled band of steel rollers. These carry solids away for up to three meters.
Her steady green light remains on display, matrimonially close to his ruby trio. Lacking the distinction of rollers, he at least rests on a figured crimson carpet. They patiently complement one another, even when silent. Mutual loyalty is the name of their game. To live inside an airport, that must be something.