From Hard Drop  Tetris Wiki
Double Triple Cannon, sometimes referred to as DT Cannon or DT, is a TSpin combo designed by player TKI. The setup is essentially a TSpin Double followed by a TSpin Triple. A player utilizes the TSpin Triple wallkick in SRS to make a TSpin Double that leads into a TSpin Triple. In Tetris variants without instant lockdown it is best to hold the soft drop button until the TSpin Double has been completed. This makes it instantly drop "through the gap" so the T tetromino doesn't rotate early and end up in the wrong spot.








Contents 
Empty Field Setups
Because so many DT Cannon setups exist, the player can choose a setup that fits the order of their opening bag of pieces. It is usually possible to hold a T through the second bag and into the third, allowing the player to make both Tspins in quick succession.
TKI's Signature
Basic DT 
Bonus TST 
IT Balance
IT Balance 1 
IT Balance 2 
IT Balance 3 
Overhang Var. 
IT Balance With 13 pieces, 
TZ Base Setups
TZ with JL overhang 
TZ with SL overhang 
TZ with OZ overhang 
TZ with JL overhang 
JO Base Setups
For these setups, build the JO base first, the fill second, and the OJ structure on the left last.
JO Base 1 
JO Base 2 
IL Base Setups
IL Base 1 
IL Base 2 
JL Base Setups
JL Base 1 
JL Base 2 
DTCannon with no T Pieces
In this setup, the player tries to use no T pieces to set up their DTCannon. It is only possible to clear this setup within 14 pieces if the second T is at the end of the second bag, but, if successful, this is the fastest DTCannon setup (in terms of piece efficiency, other setups may be faster to execute  see Efficient DTCannon Openers section below). Otherwise, the second T will be used for the upstack, reducing this setup's efficiency to the same as the rest listed here.

Other Setups
O Base 
LS Base 
LS Base 2 
JZ Base 
LZ Base 
Efficient DTCannon Openers
With the right set of pieces (one of L/J needs to come before S/Z, both if T comes too early) DTCannon can be stacked with very few key presses by taking advantage of twostep finesse. Even though a T piece is "wasted" in the stack, this build can be performed faster than many builds that are more piece efficient (such as Albatross or CSpin), thus making up for the extra pieces placed. In fact, having more pieces in the stack can sometimes be advantageous, because they can more quickly be transitioned into a 4wide stack or a Tetris stack. Note that the mirror with cannon on the right side uses more key presses, so it should be stacked on the left for optimal efficiency.

Note that the JZ Base DT Cannon results in the same stack but needs more key presses. The second bag is usually placed in one of the following ways. Sadly, none of them will work with certain piece combinations involving early T and S pieces (e.g. TSIZ).





Continuations
DTCannon is one of the most versatile openers and can be followed up in almost any style of stacking. DTREN and DTPC are thought to be some of the best counters to the dreaded 4Wide opener.
Jspin into Tspin Double




Side 4Wide (DTREN)




Tetris stacking



Lslide 
TSpin mini 
Perfect Clear followup (DTPC)



There are of course many ways to set up a PC continuation, but this way has a high success rate and is probably the most commonly employed method (as popularized by pro Japanese players like amemiyataiyou100). After the two Tspins, use the five previews to figure out the PC. Some examples:





Some more stacks that can result in a Perfect Clear after 10 lines:





And 2 stacks that can result in a Perfect Clear after 8 lines. The chances are very slim though.




CSpin followup (DTTKI)





Some stacks that can work as a base for the CSpin / Triple Double Attack:



TZ Base Continuations
The DT Cannon with TZ Base is one of few DT Cannons that will work with early T, S and Z pieces. The second bag is usually placed like in one of the following 4 ways. The OI overhang gives the best results.





Here are 2 stacks that may result in a Perfect Clear after 10 lines


And a stack that may result in a Perfect Clear after 8 lines; chances are pretty slim though.


In case of the OI overhang there's also a TSpin opportunity on the right side. Ideally, the T piece comes early in the third bag.



