If a 45° 2" Amici prism has become loose in the middle,

Product Description
Quick Solution for a Loose 45° 2" Amici Prism

Symptoms: The Amici Prism rattles or wobbles happily, sometimes audibly.
Troubleshooting: If you unscrew the top cover, you'll quickly discover the problem: The grub screws have come loose.
Solution: Using a small hexagon, you can retighten the two halves over the grub screws.

Caution: Tighten carefully and only apply a firm base tension. This will avoid damage to the mechanism and the prism.