Battle position change
A monster's battle position can be changed in one of two ways: manually or by card effect.
A manual battle position change can only be performed when the game state is open during your Main Phase. It is done by changing the battle position of 1 monster you control.
Each monster's battle position can only be changed manually once per turn.
You cannot change the battle position of a monster manually during the same turn it was Summoned, Normal Set, or declared an attack (even if the attack was negated or canceled due to a replay).
You cannot change monsters to face-down Attack Position whether manually or by a card effect.[note] Face-down Defense Position monsters are always flipped when changed to Attack Position. This change is called a Flip Summon when it's done manually.
Notes
^ Except with the effect of "Darkness Approaches".
