The Dairylea sandwich is named for one specific product because the product is the entire sandwich. This is not a generic processed-cheese build that happens to use Dairylea; it is the soft foil-wrapped triangle, mild and faintly tangy and engineered to spread without resistance, put straight onto soft white bread and nothing else. The whole character is softness chosen on purpose. There is no butter, because the triangle carries its own fat. There is no sharp counter, because the point is one gentle thing a small child will eat without negotiation. It is the lunchbox sandwich at its most undemanding, and the lack of demand is the design rather than a shortcoming.
The craft is almost the refusal of craft, which is its own kind of reliability. The triangle is formulated to stay stable: it will not split into oil and curd, will not weep, and will not sharpen no matter how long it sits warm in a school bag, so the sandwich survives a morning in a way a cut-cheese sandwich does not. It spreads edge to edge with no dragging because the fat is worked all the way through it, and that thin layer lightly seals the crumb so the bread stays soft rather than drying out by the interval. Pressed flat and cut into triangles or fingers, it holds because there is nothing wet inside to break it. The honest version is plain bread and a generous scrape of the triangle, made in under a minute and eaten without ceremony.
The variations stay inside the soft, mild frame because the format rejects anything assertive. A slice of cucumber or a little grated carrot for crunch without sharpness; a thin layer of ham turning a snack into a proper lunch; the toasted build, which pushes the same soft cheese into the toastie family and changes the rules entirely. The wider processed-cheese-spread sandwich, read from a tub rather than a triangle, is its near relative, and each of these deserves its own article rather than being crowded in here.