From Hard Drop  Tetris Wiki
Double Triple Cannon, sometimes referred to as DT Cannon or DT (known as DT砲 in Japan), 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 does not 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. The mirror with cannon on the right side uses more key presses, so it should be stacked on the left for optimal efficiency.

Depending on the bag, the alternate form might be needed.

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.
TSpin Double




Side 4Wide (DTREN)
Tetris stacking


Lslide 
TSpin Mini Single 

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:




If T comes late in the third bag but a CSpin base could be made with the other pieces, one could hold the T piece to do the CSpin TST before doing the bottom TST. Which then could be continued into a TSpin Triple Tower. Since only a single piece is needed after making the CSpin base to complete the TST in the fourth bag, the chance to be able to make a TSpin Triple Tower without wasting a T is quite good.




DTDT Cannon
DTDT Cannon, which is called "DT砲の組み替え" (lit. DT Rearrange) in the Japanese community, is a rare way for people to continue a DT cannon with another DT cannon on the opposite side of the board. Just like DTTKI, the TSpin Triple that was built on the second bag have to be done early on the third bag. Z also have to come before O.



Here are some other ways to stack:


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


