Harper & Bright Designs BARTHOLDI SOFA SET WF190610AAC Assembly Instructions Manual page 6

STEP 5 (Bench assembly)
Connect Bench seat frame (F) & Bench back frame (E) with Bolt (3)
F
3
3
3
E
STEP 6
Connect part from Step 5 & Right frame (A) with Bolt (2), Bolt (3) & Bolt (4)
3
3
4
A