Confirm that the tile is isolated
“Isolated” does not mean “unpaired.” It means the tile currently belongs to no useful meld, block, or compound shape. A 2m next to 4m already forms an inside block. A 1m beside 2m and 3m is not a disposable terminal.
How the two concepts divide the work
Edge-tile trimming focuses on discarding 1, 2, 8, or 9 when that tile is isolated or has only a weak edge connection.
Isolated-tile priority compares two close candidates: equal shanten, no more than one tile of acceptance difference, and an isolated discard on both sides. The tile with fewer development routes then leaves first.
A useful default order
Without other value, begin with non-value honors → 1 or 9 → 2 or 8 → 3 through 7. Central tiles can form more two-sided and inside blocks. This is a tie-breaker within the same main plan, not a reason to ignore a clear shanten or acceptance advantage.
Three corrections
- Visible tiles: dead neighboring tiles can erase theoretical development.
- Rules and scoring: value honors or a flush plan change priorities.
- Defense: a safe tile may matter more than offensive flexibility.
Common error
Do not apply “trim terminals” to a completed 12 edge block, a 13 inside block, or a 1234 edge run. The concept compares floaters; it does not say every 1 or 9 should disappear automatically.