Dial Indicator mount and rule support

Mount and support for use with a dial indicator and steel rule to measure flatness of a surface.

I wanted to measure the warp of my Bambu X1C print bed, but did not care for the various dial indicator mounts that attach to the extruder or its rails. Those would also show any differences caused by lack of parallelism between the rails and bed. I came up with these, which get the job done, but could use some refinement.

The support for the rule holds it perpendicular to the bed while allowing it to slide up and down, while the indicator mount slides along the rule. Waxing the rule helps if it the mount slides too stiffly. The clamping screw was just something I found in the junk drawer.

Things I would consider changing:
The clamping screw is probably not needed, as my indicators fit very tightly.
The indicator only goes into the mount about 6 mm. It holds firmly, but it just looks like making the mount a few mm taller would be an improvement.
The support for the rule is mu