Mark & Juanita wrote:

Do you have a link or some pictures of that method? I'm having a hard
time visualizing it (probably too early in the morning), but this sounds
intriguing.

Unfortunately, I don't. I'll be glad to try to provide a clearer example.

For a 3/4" thick shelf:

- Make a to 3/8" thick strip of hardwood about 1 1/2" wide.
- Drill 3/4" holes down the center of the strip, spaced where you'd like
to provide shelf options. Say... 5" apart.
- Rip the strip in half
- Glue each half to the inside end of the case, with the "half holes"
facing each other and at the same level front to back.
- Cut the shelf to the inside width of the case, minus ONE strip
thickness (3/8")and a hair.

--- From here, we have two options ----

#1:
- Mark the ends of the shelves with the appropriate radius (3/4"), and
round 3/8" of each end to mate with the "half holes"
- Install "spring strips" made of brass, or any other springy metal to
approximately center the shelf. These have to be almost flush when
installing the shelf in the case. Loose hardwood wedges can also
perform this task
- Slip the shelf into one end, and carefully pop the other end in

#2
- Make 3/8" thick "crossmembers" that fit into the holes.
- Notch the ends of the shelves square to clear the rails.
- Add a thin strip to the bottom of each shelf to contain the crossmember

The shelves can be slid to one side, removed and reconfigured at will.

I got this idea from some antique "side-by-sides" (mini desk & cabinet)
I saw at an estate auction. The method is too time consuming for
cabinetry, but looks much better in fine furniture than metal pins and
holes.

On a side note, drilling a series of holes in a planed tubafour, then
ripping it down the center, makes a GREAT glue-up bed for pipe clamps