A corner routine looks like a set of runs, but the runs are the second decision. The delivery type is chosen first, because the height and flight of the ball decide which contact points exist at all.
Flight determines where a header is possible
An in-swinging ball delivered high and towards the six-yard box arrives descending, which favours a static attacker meeting it above a defender who has been pinned. A flat, fast delivery arrives at a height where the contact is a glance rather than a full header.
Those two balls create contact zones several metres apart, and a run timed for one of them is badly wrong for the other. This is why deliveries are drilled to a repeatable flight before any attacking movement is added.
Teams with a taker who cannot reproduce the same ball consistently tend to fall back on simpler routines, because the elaborate ones depend on the delivery being predictable to the attackers, not just to the taker.
In-swinging and out-swinging solve different problems
An in-swinging corner moves towards goal, which means any touch is likely to be on target and the goalkeeper is forced to decide whether to come. It also means a defensive header only needs to interrupt the flight rather than clear the area.
An out-swinging corner moves away from goal and away from the keeper, so contact tends to be cleaner and more powerful, but the attacker must generate the direction himself. The margin for error on the header is larger.
The choice usually follows the personnel. A squad with a dominant aerial target and a reliable striker of an out-swinger will build around clean contact; a squad without one will attack the goalkeeper's zone instead.
Goalkeeper positioning is being attacked directly
A keeper starting near his line can react to a deflection but cannot claim a ball delivered into the space in front of him. A keeper starting further forward can claim but is exposed to anything played behind.
Attacking teams read that starting position during the walk-up and often signal a change of delivery accordingly. Blocking runs in front of the keeper exist to make the forward starting position unusable.
Defending sides respond by stationing a player on each post or by assigning a screen to protect the keeper's path, which reduces the number of defenders available to mark.
Movement is designed to arrive late
An attacker who is already in position when the ball is struck can be marked comfortably. The value comes from arriving into a contact zone at the moment the ball does, from a starting point the marker considered safe.
Grouped starting positions serve this purpose, since a cluster of attackers breaking in different directions forces markers to choose and creates a moment of separation for one of them.
The timing is tied to the delivery. A slower, higher ball allows longer runs from further out; a driven ball allows only a short movement, which is why the two routines look nothing alike.
Rehearsal is what makes the routine survive
Every element depends on the ball behaving as expected, which is a skill that decays without practice and is affected by wind, ball pressure and pitch conditions.
Coaches who treat corners as a weekly fixture in the training schedule accumulate a small library of routines with known success conditions rather than a single elaborate plan.
The teams that score most from corners are usually not the ones with the most inventive designs, but the ones whose delivery is repeatable enough for ordinary runs to work.