>
> Someone discussed a design feature a while back that involved
> marbles.  Somehow a marble was mounted in a slot that would
> serve to hold the saw in the till via gravity.  What was the design
> exactly?  I thought this was neat, but I never got around to doing
> anything about it.
>
> -Bob Key.

This is a new use for what any restaurant calls a tab-gripper.
We made them aons ago in school workshop: The essence is a marble
rolling down a slope, pressing against a back board.

For a tab-gripper, the board is just a pice of ply, say 6x4 inches.
The magic is in a small block of wood.
This is wide and deep enough to form a "lid" over a marble
(or ball-bearing, but marbles don't rust).

A slot, with a ramp is cut out of the block, and marble inserted,
and the block fixed to the board.

Herewith side view in bad ASCII art:
+======++===========+
|      ||           |
|      ||           |
|      ||           |
|      ||           |
|      ||           |
|      ||           |
|      ||=======    |
|      |       |    |
|      |       |    |
|      |       |    |
|      |       |    |
|      |       |    |
|      |       |    |
|      | ###   |    |
|      |##### /     |
|      | ### /      |
|      |    /       |
|      |   /        |
|      |  /         |
|      | /          |
|      | |          |
|      | +==========+
|      |
|      |
|      |
|      |
|      |
|      |
+======+

(where # is a marble.)
Not there is no gap between the block and board
at the top, but a small gap (for the paper) at the bottom.
When the paper is pushed UP into the gadget, the marble rolls
up-and-back. The vertical (gravity) force on the marble is
translated into a horizontal component by the obvliue ramp in the
block. It is this that makes the friction.

        BugBear.
        (mirror polished saws don't seem a good match for this design)