CRL Black Plastic Top Guides for 1/4" (6 mm) glass center the door glass securely in the Upper Channel, which prevents rattling and excessive side-to-side movement. Most commonly used in D603 and D613 Upper Channels. Press-fit holds Guide snugly in position. The 7/8" (22 mm) long Guides snap easily onto the top of the glass doors. A minimum of two Guides are required for each door.