Fundoshi

The T piece is stuck and cannot kick up, only rotate once left or once right.

In ARS, a fundoshi is a situation where a hole is forced in 20G because the T piece cannot be be spawned with the flat side pointing downwards, even through the use of IRS. This happens when there is a 2 unit (or more) deep hole in the 5th column. The name comes from the visual similarity with the traditional Japanese bathing suit fundoshi. The walls on either side of the 2-deep hole resemble the legs, and the T piece resembles the backside of the garment.

The imagery of the fundoshi is adopted as a logo for Pier 21's long-running The Masters tournaments, using the image of a sumo wrestler's butt. Despite this popular imagery, which technically is a related garment called a mawashi, players refer to this situation as a fundoshi rather than a mawashi.

Design Solutions

In practice strong players have no difficulty stacking in a way that prevents fundoshis from happening. However, several games (including 2 from Arika) appear to have modifications to their rules which suggests the fundoshi may have been considered an undesirable feature of the game design. These modifications give the player tools to prevent or escape a fundoshi

• Terror-Instinct gave the T-piece a floorkick, allowing it to be unstuck from a fundoshi.
• Eternal Heart allowed pieces to freely rotate during ARE, effectively opening up a 180 degrees IRS.
• Heboris allowed pieces to spawn in any of 3 different columns depending on whether DAS was charged during ARE.
• SRS has the T piece spawn with the flat side down, preventing the issue.

References

• Wikipedia article for fundoshi (bathing suit)