Keys Fitness ST-NBB Owner's Manual page 8

Assembly
NOTE: Hand tighten bolts and nylon nuts until machine is fully assembled.
STEP 4
Attach the backrest support (#9) to the pivot on the Main Frame (#5)
.
Align Backrest Pad (#13) to backrest support (#9) and secure with
four M6X40 Bolts (#29), and four D6.5 washers (#31).
Place the seat pad (#14) on bracket of the Main Frame (#5) and
secure with four M6X15 Bolts (#30), and four D6.5 washers (#31).
And adjust the height with the backrest Adjustment Bar (#04).
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