Thank you for your inquiry regarding this item from Prime-Line Products. To remove the roller assembly, remove the installation screw found at the bottom. Slide the roller assembly towards the center of the door, then pull out. The new roller assembly needs to drop in the opening and slid towards the outer left and right corners until the screw holes line up. Make sure the adjustment screw protrudes through a hole that adjoins the bottom rail with the side stile. Install the installation screw through the bottom of the door and into the roller assembly housing. After installing the door into the door frame, adjust the roller assembly to raise the door off of the track, then level by adjusting both roller adjustment screws on edges of door.
For additional questions regarding this item, or any other product manufactured by Prime-Line Products, please call their toll free number at (877) 649-9740, or contact them by email at firstname.lastname@example.org