What substance is commonly used to prevent scope rings from slipping against each other?

The correct answer is rosin, which is commonly used to prevent scope rings from slipping against each other. Rosin provides a sticky surface when applied, which increases friction between the scope and the rings. This added friction helps to secure the scope in place, maintaining proper alignment and preventing any unwanted movement that could affect accuracy when aiming.

Rosin is particularly favored because it does not make the surfaces permanently bonded, allowing for adjustments or removals without excessive difficulty. In contrast, substances like wax, oil, or glue can either reduce friction (and thus can make slipping more likely) or create a more permanent bond that could complicate future adjustments.