Stonehenge matters architecturally less for the size of its stones than for the way they are joined. Its core unit is the trilithon: two vertical stones (sarsens) carrying a horizontal lintel. This is the post-and-lintel system in its purest form — but here the logic of timber carpentry has been transferred into stone.

The underside of each lintel carries carved hollows (mortises) that drop onto projecting knobs (tenons) on the tops of the uprights, locking the lintel against displacement. In the outer sarsen ring, lintels are joined end to end by tongue-and-groove connections to form a continuous, curved stone hoop. The upper faces of the lintels were dressed to stay level despite the sloping ground, while the uprights taper slightly upward — an entasis-like correction attentive to perceived balance.

The sarsens, weighing around 25 tonnes, came from the region; the smaller "bluestones" were brought from the Preseli Hills in Wales, hundreds of kilometres away — showing that the choice and logistics of stone were themselves design decisions. Stonehenge thus represents the moment the megalithic tradition evolves from a loose array of standing stones into a structural system with its joints resolved: stone is no longer merely raised, but assembled with carpenter-like connections.