Discovered in Super Smash Bros. Melee, the Boost Grab is a very quick and useful form of Dash attack canceling. By completely canceling the Dash Attack, the user suffers far less Lag. This move is more useful than a Dash Attack if you want to prevent yourself from getting hit. Although this attack looks useless, leading you to think that you can just press Z to save time, the Boost Grab is a very good Mindgame.
The grab can be replaced with an up-smash to preform a Dash attack canceled up smash (DACUS)
Performing a Boost Grab
To perform the Boost Grab, you must first Dash. Then, press A while dashing to preform a Dash Attack, then press L,R, or Z immediately within the first frame to grab. If done correctly, the Dash Attack will be canceled and you'll skip straight to a grab. If you skip the first frame of the Dash Attack and then grab, then you won't do a Boost Grab and you'll suffer due to the lag of the Dash Attack.
A good method of practicing this is to go into Practice Mode and choose Mario. Attempt to boost grab, and if Mario's Dash Attack sound is accompanied by a grab, the Boost Grab was successful. This can be practiced with Wolf in SSBB because his boost grab retains his dash attack sound.