Locate the center support slat and one of the barrel nuts. With the screwdriver slot facing up, place the nut inside the hole on the slat's surface. Attach the slat to the right bed rail with a hex socket head bolt by threading into the barrel nut. Tighten with an Allen key.
Place barrel nuts into the holes located on both ends of the bed's right rail. Attach the right side rail to the headboard and footboard with hex socket head bolts by threading into the barrel nuts. Tighten with an Allen key.
Locate the additional support slats. Position the assembled bed on its side and push the slats into the grooves along the right bed rail. Each slat dowel should fit securely in the corresponding holes.
Place barrel nuts into the holes located on both ends of the bed's left rail. Thread hex socket head bolts through the holes and into the barrel nuts to attach the left railing to the center support board. Attach the left side rail to the headboard and footboard with hex socket head bolts by threading into the barrel nuts.
Before tightening the railing, use hex socket head bolts to attach the guardrails to the headboard. Secure the opposite ends of each guardrail to the respective hole in the right and left side rails with hex socket head bolts. Tighten all bolts with an Allen key.