This was a very long drawn out project. I made the posts & rails, cut & fit all 66 sq. spindles, then got waylayed by other projects. For over a year! Once I got back to it I still had not figured out the best way to attach the sideboards to the Head & footboards. I wanted something very strong, but not obvious. My son had been playing with a handfull of “super” magnets one day & left them laying out. HMMMMMM?!? A little experimentation & EUREKA!! The “thru” tenons in the second photo are fake. They hide two 3/8”x12” bolts that connect to blind nuts morticed way back in the side rails. The fake tenon ends have dowels glued into shallow holes to center them in the bolt access holes. I installed T nuts & bolts (for adjustment) with the super magnets epoxied to the heads. That’s the third photo. They do not have to touch the bolt heads, just get close & they snap into place. Looks great & the bed is rock solid. The posts themselves are lock mitered 4” sq. with blocking glued inside at the tenon joints.