Filing a negative carrier?
I make rough black borders without involving modification of the carrier. I work out the image size( normally constant for several prints), and then produce a black card mask with the border cut into it. This sits in the easel on top of the paper which is then exposed to make the border, card removed, then image exposed. When preparing the mask, I cut one side, then cover the cut on front and rear with transparent tape. Doing this one side at a time keeps the image area mask suspended within the outer frame. Depending on how you set up the image size, you may need to print the border with the easel frame raised. The whole process is easy to do. The important part is keeping paper and mask aligned in the easel. I wouldn't recommend this for producing fine black borders! Alex