MDF (Mini Double Fractal) is an opener created by the player benmuga which makes a TSM or a 1 line skim followed up by a TSD and a Perfect Clear with I J or L ending. If PC is not possible then starting making a fractal or making 2 TSD without the fractal formation.

MDF can be used in various piece patterns always following the next rules:

1.- If L is used first, J must be used after Z. 2.- if Z is used first, S must be used after L.

Those rules applies not exactly right after "Z" or "L" are placed but they must follow that order independant of the other pieces on the same bag, and both rules are expected to be on different bags.

Some tips to memorize the opener easily are: 1.- DAS O all the way to one of the walls 2.- If O is placed on the right wall, Z comes next to O 3.- With the example of tip 2, on the left wall L and S comes together

In case if T is the first piece you need to place because you have an I piece right after, wasting T would be the only option to make the opener, and the only position for the opener that it have is placing the piece right where it spawns or one space to the right, depending on the pieces after I. After this you must hold I and follow the rules above.