#2 ="ankle" buckle
#3 = "instep" buckle
#3 and #4 are on the "clog" of the boot.
#2 and #1 are on the cuff.
The ramp angle of the boot board affects how strongly the top of your foot contacts
the top of the boot under the instep buckle. A bootfitter can alter this angle by grinding
the bottom of the boot board. You do need contact to tip the boot and the ski with
precision, but too much contact that feels like "pressure" is not good.
There are arteries on top of your foot. People are talking about how these arteries
provide warm blood to the toes, and how clamping down hard on the instep buckle
might impact the delivery of this warm blood.
Also important are the nerves on top of the foot. Clamp down on them and everything they connect with goes numb. Pinched nerves can produce numbness, pain, stinging, and the feeling of burning. Nerves are yellow in this image.
There are blood vessels and nerves embedded in the middle of the foot and around the ankle bones that sometimes get pinched by ski boots, causing numbness, cold, and pain. A good bootfitter can address these issues by working with the custom footbed, the liner, and the shell.
For those reading here who are new to boot adjustments, many of these adjustments come "free" with the purchase of a boot (not the custom footbed, though). It also takes some time skiing in the boots to diagnose the issues, and several trips back to the original bootfitter are often necessary to get this all sorted. These visits and adjustments are often free, since after all you paid a fortune for the boot in the first place.