Someone once asked me why I like boxes so much. I think I answered with this little zinger: "I don't know." Anyway, I like making them, and I try to incorporate them in my other, "non-box" work whenever I can. Maybe I just think little boxes are friendly, somehow. More to the point (if there ever was one in the first place), here is how I make the little pegs on the Mandell Bed and the Double-Trestle Desk.
I begin by laying out and cutting a shallow, square mortise when the peg will go. This is done before the piece is cut out or shaped in any way, so I don't lose my reference edges. I then shape, sand, glue, and finish the piece as necessary. (Pre-finishing the piece will help later on. )
Once the finish has dried and cured, I can start work on the pegs themselves. I drill out the remainder of the mortise (through the tenon in the mating piece), being careful not to disturb the walls of the square mortise. Drilling all the way through the piece would be bad. Very Bad.
The next step is to finish squaring up the mortise so it can accept the square peg. Some people just drill a hole, then square up the "face" of the hole to make the mortise. I think it is actually easier to square up the entire mortise, so you don't have to taper the peg.
Detail of mortises. The mortise on the right has been fully chopped and cleaned out, while the one on the left has only been drilled.
After carefully test-fitting the peg, drop in a little dab of yellow glue...
...and tap it home. Having pre-finished the piece helps here because any glue squeeze-out can simply be wiped up, rather than trying to sand and make a mess of the whole thing.
Next, I use a flush-cut saw on a little scrap of plywood to cut the peg about an 1/8" proud of the surface of the workpiece.
a couple of rough-cut pegs.
Once all the pegs are fit, glued in, and cut to length, I mask off the areas around the pegs with several layers of blue painters tape. This protect the workpiece from getting scratched during shaping and sanding.
With plenty of masking tape in place to protect the piece, I begin shaping each peg. I do the initial rough-shaping with a rasp...
Pegs after rough-shaping.
...then refine the shape with a small file.
Once the pegs are filed, I further shape them with 220-grit sandpaper, then polish them with 400-, 600-, 800-, 1200-, 1500-, 1800-, and 2400-grit paper. A final buffing is done with a white abrasive pad.
Finally, the tape is removed, a thin coat of wax is applied and buffed out, and the piece is ready to go. All together, each peg requires about 45 minutes to mortise, fit, glue, and shape. (There were twenty-four pegs total for this particular project. The Double-Trestle Desk has sixty-four. 64 x .75 = 48 hours of labor)
The reason for doing all this is not strictly for decoration. Rather, each peg serves as a physical "lock" to the joint, adding plenty of mechanical strength to the already-strong chemical strength of the glue in the joint.