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Got your "Ducks in a row?"
"Bolsters" is correct. The word comes from old English/Dutch and has many meanings including knife and spreading pressure:
Wiktionary "bolster"
The folding knife...

A very nice fitting of the onlays! you took the time to match the scales to the metal bits before adhering them.
An addition for future works:
If you polish plexiglas/acrylic be careful not to heat...