Ricoh D131 Service Manual page 1363

Booklet Stapling (B804 Only)
7:
The bottom fence [1] raises the stack to the prescribed fold position [2].
8:
The fold plate [3] moves to the left and advances 1/3 its maximum horizontal stroke and
exerts 20 kg (44 lb.) of pressure at the fold rollers [4].
9:
With the fold plate pushing the stack into nip of the fold rollers [5], the fold rollers begin to
rotate and fold the stack as it feeds out.
SM 57 B804/B805/D373/D374/D612