Bedding
How tightly the rifle's action sits inside the stock or chassis. Glass bedding, pillar bedding, and full chassis systems all aim for the same result: zero movement between action and rest.
A loose action in a stock will shift point of impact between shots and between range trips. Bedding eliminates that play. Glass bedding pours epoxy around the action to take a perfect impression. Pillar bedding adds aluminum or steel sleeves around the action screws so screw torque doesn’t compress wood or plastic.
Chassis systems skip the question entirely — the action drops into a machined aluminum cradle with no flex.