This is so easy to make, taking less than 30 minutes. Using two 8′ 1×4″ pieces from The Home Depot, each was cut at 5′ and the remaining three feet of each piece cut in half (they can do this at The Home Depot for you).
Pilot holes were drilled at the ends of each smaller piece – these are the rungs in the ladder, so it is important that each piece is exactly the same size. Next drill holes 12 inches apart on the 5′ pieces, starting at 18″ of one end. This way you will have four rungs, and the one closest to the bottom can still accomodate a blanket at 18″ off the floor.
Once all pilot holes are drilled, screw the rungs into the side pieces (one side at a time) using 1.5″ #8 screws. Paint or stain as you like.