The basic construction uses 1 inch diameter hardwood dowel rod, as shown in Figure 14.
Figure 14 - 1″ Hardwood dowel rod
To ensure that the construction of the railing is perfectly level a template should be made using a scrap piece of lumber or plywood, as shown in Figure 15.
Figure 15 - Template for loft bed railing
The railing is connected to the front using two 2 x 4 support posts on each end and a middle 2 x 4 support, as shown in Figures 16 and 17. The front 2 x 4 support posts should extend 14 inches above the top of the horizontal loft bed frame. This allows 8 inches for the mattress and 6 inches for the railing above the top of the mattress.
Figure 16 - Front loft bed railing assembly
Drill all the holes in the 2 x 4 support posts for the dowel railing, using the template (Figure 15), before mounting the supports to the loft bed frame. The holes only need to be 1/2 inch deep, but can be deeper if you so desire. Use yellow carpenter's glue to glue the dowel rods into the holes. A 1 inch brad can be used through the side of the 2 x 4 and 1 x 2 lumber to provide added fastening for the dowel rods.
Note: When drilling the holes for the dowel rod, ensure that the drill bit is perfectly perpendicular to the lumber. Holes that are drilled at an angle make insertion of the dowel rods very difficult.
Use yellow carpenter's glue and 2 1/2 inch wood screws, inserted from the back side to hold the front support posts to the original support posts as shown in Figure 5.
The open side railing is made by drilling holes in the top end of the support post that does not have a connecting wall. The other side of the rails is supported in a piece of 1 x 2 lumber. Fourteen (14) inches less the thickness of the bed deck lumber, as shown in Figure 17.
Figure 17 - Side loft bed railing assembly
Screw the railing support wall board to the wall. If there isn't a stud behind the board, use drywall anchors and screws to ensure that the railing is properly fastened.