SCOTU
Smash Hero
The following shows the sweetspot grab boxen for all characters. A character grabs the edge by completing the following conditions:
1. Being in a state in which one can grab the edge (i.e. on your way down from a jump)
2. Having the sweetspot box in front of you overlap the edge (edges shown below).
3. Having the sweetspot box behind you not overlap the edge (unless using a move you can grab behind you from - i.e. CF's Up-b).
Look a few posts down for the rest
1. Being in a state in which one can grab the edge (i.e. on your way down from a jump)
2. Having the sweetspot box in front of you overlap the edge (edges shown below).
3. Having the sweetspot box behind you not overlap the edge (unless using a move you can grab behind you from - i.e. CF's Up-b).
Look a few posts down for the rest