Castles · 文鎮囲い
Paperweight.
Every piece between the lances lifted off the bottom rank: silver, king, two golds and silver in one row on the second rank, so the rook can run along the first.
How it goes together
Build the Boat castle, then clear the bottom rank. The bishop leaves 8h for 6f, the left knight jumps to 7g, the left silver takes the bishop’s old square on 8h, and the 6i gold steps up to 6h beside the 5h gold. On the other side the right knight goes to 3g. Silver 8h, king 7h, golds 6h and 5h and silver 4h now stand in one line, like the long paperweight a calligrapher lays across the paper, and only the two lances are left on the bottom rank. The two golds guard each other, and the 8h silver and the 6h gold both guard the 7g knight.
The Paperweight starts as a Boat: the first seven moves below are that castle, and nine more clear the bottom rank.
Move by move
Black only, from the start position: the Boat castle’s seven moves, then nine more in the Japan Shogi Association’s column’s order, which push the rook pawn and the edge pawn and lift every piece between the lances off the bottom rank. The column plays the rook pawn second; here it waits until the Boat is built.
Step through the moves, or press play.
Tap a move to jump to it. Arrow keys work once the board has focus.
Sixteen moves. The castle is there for what comes next: the rook drops back to 2i, the lance steps up to 9h, and the rook runs along the empty bottom rank to 9i, behind the lance. That is the Subway Rook.
What it is good against
It is what makes the Subway Rook possible, and ja.wikipedia counts it strong in defence. ja.wikipedia says the Subway Rook works especially well against an Anaguma, and the JSA column calls it a good choice against the Fujii System too.
Where it breaks
Moves and flexibility. Every piece on the bottom rank has to move first, so it takes many moves and fixes the shape, which is why ja.wikipedia says the Subway Rook is not often played. Once the rook has gone to the far edge, king and rook stand close together, and an early check can put you on the defence (shogi-gym). Fujii Takeshi disliked the shape: he said it looked like a paperweight, and from that remark it also came to be called 文鎮囲い, the paperweight castle.
When to build it
A static rook against a ranging rook that castles slowly: the JSA column shows it against an Anaguma and against a Mino whose owner had pushed the edge pawn early, and shogi-gym adds a game against a Right King, whose king also sits near the edge. It goes with the Subway Rook every time.
Build it at the board.
The app’s lesson walks the king into a Mino one step at a time, and its review names the castle you were building when a game turned.