Costway SP37675 Manual Del Usuario página 13

STEP 4
Connect the main frame assembly (1) with the aluminum rail (7), and fix
them with the outer hexagonal lock nut (21), flat gasket (3) and outer
hexagon screw (22).
Insert the lock pin (23)
Screw the locking knob (24) into the nut from above, making sure that it
is tightened in place.
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