The Mull-It-OverĀ® Mullion Trim Cap stems a deep understanding of building construction and a need to resolve the key six inches of space around the perimeter of every glass building. The Mull-It-Over mullion trim cap system re-creates the sound- deadening capability of a well-constructed drywall partition all the way out to the face of the glass. Whether the installation is in a patient room, a boardroom or a bedroom, noise transfer can now be resolved with Mull-It-Over.