Lay out the support beams parallel to each other on the thin side. Insert barrel nuts into the holes on the ends of the beams with the groove facing out. Align the holes on the arm and the beam. Using the Allen wrench and confirmat screws, attach the arm to the beam by driving the screw through the arm into the barrel nut on the beam. Tighten the nuts with a screwdriver, but make sure that the frame is still slightly loose.
Lay the decks back to back on the floor. Put a clevis pin and a cotter pin into each hinge point. Secure the slide rollers on the back deck by using additional clevis and cotter pins.
Place the assembled decks carefully onto the frame, making sure the slide rollers line up with the grooves in the arms. Line up the top rollers with the vertical grooves and the bottom rollers with the horizontal grooves.
Tighten the screws on the beams, but do not overtighten them. Push the frame into a sitting position and place the futon on the frame.