Ledge-canceling
In Super Smash Bros. Melee, a ledge-cancel is a complex command that exploits the physics of momentum and traction, allowing a character to "cancel" the "lag" after an aerial attack, ending in the "falling" state.
A character ledge-cancels an aerial attack in three steps.
1. From aerial attack state, the character cancels the aerial attack (in the form of a land-cancel) by landing that attack on the ground or ledge, entering that attack's landing state.
2. The character slides on the ground or ledge in landing state, with a vector determined by his: a) vector upon landing in relation to the angle of the ground or ledg; b) directional input; and: c) traction.
3. The character fall-cancels the slide by sliding off a ledge, entering the falling state.
By ledge-canceling a character can potentially execute two aerial attacks or an aerial attack then B attack in quick succession with it's combination of canceled move lag and canceled landing lag. A minimum number of frames between attacks of 3+the number of frames it takes the second attack to produce a hitbox is possible if the character land-cancels an attack after one frame of hitbox, then fall-cancels the landing after one frame of by sliding off a ledge, then attacks on the first frame of falling.
A character can also ledge-cancel and aerial attack into an air jump or air dodge.
Aerial attacks can be canceled on any of their frames. This means that an attack can be canceled (and subsequently ledge-canceled) before a hitbox appears.
A character can ledge-cancel an attack if he is facing towards or away from the ledge.
A character can also use ledge-canceling to end in their ledge state (the state in which they appear to be teetering almost off balance on the ledge). This is done by facing in the direction of the ledge to be canceled on when landing and inputting no directional influence when on the last frame of sliding, before you would normally fall, so that when you slide to the ledge, instead of DIing off you enter ledge state.
Similar to falling ledge-cancels, a character can use standing ledge-cancels not only to cancel an aerial attack into a B attack or air-jump, but also a ground attack, or grab.