Marth Tech: Shai Drop
Description / How To Perform
Shai dropping is a type of Shield Droping used to fall through a platform quickly during a dash. The most common method of doing so is buffering down between 1 to 3 frames before pressing a shield button while dashing.
There are a few different methods for Shai Dropping as well. What I do personally is rolling the analog stick from holding full left or right towards the 45% downwards angle on that side. This requires you to either be already holding Left or Right when initiating your shield, or for you to buffer Left or Right during Hit-Stun. Conveniently enough, you'll often already be holding either Left or Right on a platform while shielding, because shielding out of a Dash is common.
Usefulness: (Extremely Useful)
You may want to use your Light Shield when Shai Dropping to avoid accidental airdodges.
To see full details on Shai Dropping, including all methods of doing them, there's a great smashboards thread describing the technique fully.