The 30 - year - old apartment veranda shutters are difficult to move and we decided to replace the door roller as we can get out of time. I came upon this looking for something similar to the previous one. Although it was slightly larger in size than the previous one, it can be used without trouble. At the time of replacement, first remove the old one, then loosen a little of this new screw, then fasten it on the metal part and exchange it in the form of tightening the screw, but I do not know it at first, I dropped the lower half by removing all the screws and lost it. I was saved because I accidentally bought extra. It may be a matter of course to the merchant's person, but it is a beginner.