Sheathing the Sword is a concept that encompasses sword forms.
When victory must be won at all costs, the swordsman allows the opponent's weapon, usually a sword, to be sheathed in his own body. By luring the enemy into making a cut, the enemy comes close enough to be killed.
Lan Mandragoran first taught this concept to Rand al'Thor as Rand was leaving Fal Dara. Rand first sees this in use when Ingtar Shinowa defended a narrow alley to the death so that Rand and his companions can escape Falme. Later, in the battle over Falme, Rand realizes he is fighting Ishamael to a stalemate, and he is running out of time. Rand used Heron Wading in the Rushes to allow the Betrayer of Hope to stab him. This lured Ishamael within Rand's cutting range, allowing Rand to finish him off.
Lan also utilizes Sheathing the Sword in his duel against Demandred at the Field of Merrilor, allowing him to stab the Forsaken through the throat.