Focusing rail assembly for Omega D2. Comes unassembled. First 3 pictures show what it looks like assembled. To put it together, slide the rails into the housing with the slots pointed toward the back of the enlarger. There are marks on the rails to show where to align it. The impressions in the rails from the set screws (shown on the back of the housing) are also a guide of where it should fit. Screws that hold it onto the enlarger are included.